Yeah I wouldn't worry about a long frame, I'm 6'3" and 14 stone and I've got a short 07 python which feels fine.
As for Trials UK, don't even go there! When you get validated you'll probably find some good stuff in the for sale but it depends on how big your budget is, seen as you've ridden before there's no reason to not get a new frame as you don't have to worry bout trashing something whilst learning like most of the noobs on here.