I work on iPlayer. The new responsive design website will use the HTML5 + HLS player on iOS. Currently on Android and desktop we are using Flash + HDS/RTMP, but it's possible this will change in the future. The reason we are using Flash at the moment is partly to do with content protection (which involves negotiations with the content rights holder), and partly to do with the fact that there isn't a standard streaming mechanism across the different platforms we need to support. We would likely move to MPEG-DASH, for example, if it's more widely adopted across the platforms.