Just to complete the circle for anyone who cares. As I say I moved the cable box diwbstairs, which left me having to split the cable feed there. This seems to have been causing the issue as I moved the router upstairs to the other cable feed which the virgin engineer out in to install our TV box (ha). Seems to have stopped the router crashing and the box now works. Kind of get why the router stopped working properly because of the power levels (though it was attached to an attenuator downstairs, dies thisnreduce your signal?) Whereas upstairs it isn't. Still don't quite get why the box refused to pick up an IP address but don't particularly care now I can stream in it again. Thanks for your suggestions, regardless.