I fully agree with the comment that buying a cheap 29er will probably unfairly bias the experience, but here goes:
Amazon currently sell a Reebok Twenty 9er at £150.00. Yes, it will be rudimentary and heavy, but saying that, it has 21 gears and a sus fork, so it may be more of a realistic prospect (than a SS) for those like me with weak legs in a hilly area. It could also be a decent emergency bike when the prime is in the 'shop.
I too am looking at a 29er at the moment as I am 6'5" and 14.5 stone. I think my weight may countermand any shortfall due to the increased wheel-size and I do like the sound of the better rolling thing. One (newbie) question though: why do all the frame-sizes seem to stop at 20"? I currently have a 22" HT and this is a little small in truth. Is it simply a case of wheel clearance? Would I fit OK on a 20" 29er? I know that the published frame size is often scant indication of the actual size of the bike, but two inches is still two inches!
Any advice welcome, including a place near Stockport to test one out.