It would seem that the crack is by a weld near the headtube, where the bottom tube meets the top tube. Its not all the way around but goes just the width of the weld. The chainstay crack is about 5mm long, starting at a pre-drilled hole and working along. According to the seller its been fine with his riding for the last 6 months, neither crack has got any bigger. I think I might go for it and then when it breaks Ill just buy another second hand frame. Its the best deal Ive been offered so far by a long way. Thanks for all the info folks, its really useful and your all very helpful