iphone 4 video streaming issue with BT home hub 3 wifi

Having switched to BT total broadband (UK) a few weeks ago my wife and I have both had issues streaming any kind of video (youtube, facebook videos, webpage inbedded videos) with each of our iphone 4 devices. Its a BT home hub 3 (their latest model) and it only seems to affect video playing, surfing the web is fine, facebook is ok and all apps work ok so i cannot work out why this is happening.

Most of the time a video will play around 5 seconds and then stop and look like its loading without the buffer bar actually going up, sometimes it will boot me off the router and not reconnect and sometimes it will load and play the video with a few stop and starts along the way.

I have spent ages on the phone to BT trying to resolve the issue but they have exhausted all possible ideas that could be connected to the router. However, i borrowed a friends BT home hub 2 and used it for three or four days without any problem at all, videos loaded and played uninterupted just as they should which has puzzled me even more.

Any help would be greatly appreciated as its driving me up the wall, also my wife has just started an online course which relies on video playback so we really need the situation alleviated!

Cheers, Martin