diff --git a/README.md b/README.md
index 2b38265713..ae1cd17c9a 100644
--- a/README.md
+++ b/README.md
@@ -25,9 +25,14 @@ You can use matrix-react-sdk directly, but to do this you would have to provide
 How to customise the SDK
 ========================
 
-The SDK uses the 'atomic' design pattern as seen at http://patternlab.io to
+The SDK formerly used the 'atomic' design pattern as seen at http://patternlab.io to
 encourage a very modular and reusable architecture, making it easy to
 customise and use UI widgets independently of the rest of the SDK and your app.
+
+So unfortunately at the moment this document does not describe how to customize your UI!
+
+###This is the old description for the atomic design pattern:
+
 In practice this means:
 
  * The UI of the app is strictly split up into a hierarchy of components.
diff --git a/src/components/structures/MatrixChat.js b/src/components/structures/MatrixChat.js
index 09583951fc..fca688ee15 100644
--- a/src/components/structures/MatrixChat.js
+++ b/src/components/structures/MatrixChat.js
@@ -1181,7 +1181,7 @@ module.exports = React.createClass({
                     defaultIsUrl={this.props.config.default_is_url}
                     customHsUrl={this.getCurrentHsUrl()}
                     customIsUrl={this.getCurrentIsUrl()}
-                    onForgotPasswordClick={this.onForgotPasswordClick} 
+                    onForgotPasswordClick={this.onForgotPasswordClick}
                     onLoginAsGuestClick={this.props.enableGuest && this.props.config && this.props.config.default_hs_url ? this._registerAsGuest.bind(this, true) : undefined}
                     onCancelClick={ this.state.guestCreds ? this.onReturnToGuestClick : null }
                     />
diff --git a/src/components/structures/MessagePanel.js b/src/components/structures/MessagePanel.js
index 49f4783eaa..16b4892bc0 100644
--- a/src/components/structures/MessagePanel.js
+++ b/src/components/structures/MessagePanel.js
@@ -85,6 +85,12 @@ module.exports = React.createClass({
         // opaque readreceipt info for each userId; used by ReadReceiptMarker
         // to manage its animations
         this._readReceiptMap = {};
+
+        this._isMounted = true;
+    },
+
+    componentWillUnmount: function() {
+        this._isMounted = false;
     },
 
     /* get the DOM node representing the given event */
@@ -201,6 +207,10 @@ module.exports = React.createClass({
         }
     },
 
+    _isUnmounting: function() {
+        return !this._isMounted;
+    },
+
     _getEventTiles: function() {
         var EventTile = sdk.getComponent('rooms.EventTile');
 
@@ -351,6 +361,7 @@ module.exports = React.createClass({
                         onWidgetLoad={this._onWidgetLoad}
                         readReceipts={readReceipts}
                         readReceiptMap={this._readReceiptMap}
+                        checkUnmounting={this._isUnmounting}
                         eventSendStatus={mxEv.status}
                         last={last} isSelectedEvent={highlight}/>
                 </li>
diff --git a/src/components/structures/RoomView.js b/src/components/structures/RoomView.js
index ac848030af..9b8322f69e 100644
--- a/src/components/structures/RoomView.js
+++ b/src/components/structures/RoomView.js
@@ -210,7 +210,7 @@ module.exports = React.createClass({
             MatrixClientPeg.get().removeListener("RoomState.members", this.onRoomStateMember);
         }
 
-        window.removeEventListener('resize', this.onResize);        
+        window.removeEventListener('resize', this.onResize);
 
         // no need to do this as Dir & Settings are now overlays. It just burnt CPU.
         // console.log("Tinter.tint from RoomView.unmount");
@@ -878,7 +878,7 @@ module.exports = React.createClass({
         this.setState({
             uploadingRoomSettings: true,
         });
-        
+
         var newName = this.refs.header.getEditedName();
         if (newName !== undefined) {
             this.refs.room_settings.setName(newName);
@@ -887,7 +887,7 @@ module.exports = React.createClass({
         if (newTopic !== undefined) {
             this.refs.room_settings.setTopic(newTopic);
         }
-        
+
         this.refs.room_settings.save().then((results) => {
             var fails = results.filter(function(result) { return result.state !== "fulfilled" });
             console.log("Settings saved with %s errors", fails.length);
@@ -1229,7 +1229,7 @@ module.exports = React.createClass({
                                 rightPanelCollapsed={ this.props.rightPanelCollapsed }
                             />
                             <div className="mx_RoomView_auxPanel">
-                                <RoomPreviewBar onJoinClick={ this.onJoinButtonClicked } 
+                                <RoomPreviewBar onJoinClick={ this.onJoinButtonClicked }
                                                 onRejectClick={ this.onRejectThreepidInviteButtonClicked }
                                                 canJoin={ true } canPreview={ false }
                                                 spinner={this.state.joining}
@@ -1266,7 +1266,7 @@ module.exports = React.createClass({
                     <div className="mx_RoomView">
                         <RoomHeader ref="header" room={this.state.room}/>
                         <div className="mx_RoomView_auxPanel">
-                            <RoomPreviewBar onJoinClick={ this.onJoinButtonClicked } 
+                            <RoomPreviewBar onJoinClick={ this.onJoinButtonClicked }
                                             onRejectClick={ this.onRejectButtonClicked }
                                             inviterName={ inviterName }
                                             canJoin={ true } canPreview={ false }
@@ -1402,8 +1402,8 @@ module.exports = React.createClass({
             }
             voiceMuteButton =
                 <div className="mx_RoomView_voipButton" onClick={this.onMuteAudioClick}>
-                    <img src={call.isMicrophoneMuted() ? "img/voice-unmute.svg" : "img/voice-mute.svg"} 
-                         alt={call.isMicrophoneMuted() ? "Click to unmute audio" : "Click to mute audio"} 
+                    <img src={call.isMicrophoneMuted() ? "img/voice-unmute.svg" : "img/voice-mute.svg"}
+                         alt={call.isMicrophoneMuted() ? "Click to unmute audio" : "Click to mute audio"}
                          width="21" height="26"/>
                 </div>
 
diff --git a/src/components/views/rooms/EventTile.js b/src/components/views/rooms/EventTile.js
index 5c70c9da10..7db8af9312 100644
--- a/src/components/views/rooms/EventTile.js
+++ b/src/components/views/rooms/EventTile.js
@@ -116,6 +116,12 @@ module.exports = React.createClass({
          */
         readReceiptMap: React.PropTypes.object,
 
+        /* A function which is used to check if the parent panel is being
+         * unmounted, to avoid unnecessary work. Should return true if we
+         * are being unmounted.
+         */
+        checkUnmounting: React.PropTypes.func,
+
         /* the status of this event - ie, mxEvent.status. Denormalised to here so
          * that we can tell when it changes. */
         eventSendStatus: React.PropTypes.string,
@@ -261,6 +267,7 @@ module.exports = React.createClass({
                 <ReadReceiptMarker key={userId} member={member}
                     leftOffset={left} hidden={hidden}
                     readReceiptInfo={readReceiptInfo}
+                    checkUnmounting={this.props.checkUnmounting}
                     suppressAnimation={this._suppressReadReceiptAnimation}
                     onClick={this.toggleAllReadAvatars}
                 />
diff --git a/src/components/views/rooms/ReadReceiptMarker.js b/src/components/views/rooms/ReadReceiptMarker.js
index bc433b8bd0..d40b2f5f8d 100644
--- a/src/components/views/rooms/ReadReceiptMarker.js
+++ b/src/components/views/rooms/ReadReceiptMarker.js
@@ -53,6 +53,11 @@ module.exports = React.createClass({
         // this room
         readReceiptInfo: React.PropTypes.object,
 
+        // A function which is used to check if the parent panel is being
+        // unmounted, to avoid unnecessary work. Should return true if we
+        // are being unmounted.
+        checkUnmounting: React.PropTypes.func,
+
         // callback for clicks on this RR
         onClick: React.PropTypes.func,
     },
@@ -81,6 +86,13 @@ module.exports = React.createClass({
             return;
         }
 
+        // checking the DOM properties can force a re-layout, which can be
+        // quite expensive; so if the parent messagepanel is being unmounted,
+        // then don't bother with this.
+        if (this.props.checkUnmounting && this.props.checkUnmounting()) {
+            return;
+        }
+
         var avatarNode = ReactDOM.findDOMNode(this);
         rrInfo.top = avatarNode.offsetTop;
         rrInfo.left = avatarNode.offsetLeft;
diff --git a/src/components/views/rooms/RoomPreviewBar.js b/src/components/views/rooms/RoomPreviewBar.js
index 9f095143d1..93f5b5161c 100644
--- a/src/components/views/rooms/RoomPreviewBar.js
+++ b/src/components/views/rooms/RoomPreviewBar.js
@@ -97,7 +97,7 @@ module.exports = React.createClass({
                             </div>
                             <div className="mx_RoomPreviewBar_warningText">
                                 This invitation was sent to <b><span className="email">{this.props.invitedEmail}</span></b>, which is not associated with this account.<br/>
-                                You may wish to login with a different account, or add this email to your this account.
+                                You may wish to login with a different account, or add this email to this account.
                             </div>
                         </div>
                 }