Purely because I believe that issues are best resolved in the open, rather than in private email conversations so that others can read the answers too, I'll also answer! Yes I believe that car would be, once the boot floor was sorted out. I believe the seat rails have to be welded in to have a seat, otherwise you'd not have anywhere to put your seat!
If you're looking for cars for sale its best to look at
http://clubmansrallycross.weebly.com/classifieds.html
There's a good mix of cars on there, including I believe the one you were referring to?