Thanks for your response! We're using a variety of devices but predominantly iPads and Surfaces. It's becoming more of an issue as our IT committee are pushing more and more towards byod - we've decided that because of this Screen Share issue, we're not ready.
Interesting point about 2.4 vs 5ghz connection. I will definitely feed this info back to our network manager to see if that can help. We are predominantly 5ghz now but still have some ap's with 2.4 connection so that could well be causing a problem.
The issues we are experiencing are consistent with pretty much any device, whether that be a Surface, iPad, iPhone or from a Chrome browser which certainly points towards the network, or to the hardware itself. It seems that using the 'reset' option in the AM40 settings, under the screenshare option enables the connection to work fine for a short time, to which it eventually deteriorates over time - I can't tell our staff to constantly be doing this though, it's one of those features that should 'just work'.
I'll report back when we explore forcing 5ghz!