I probably would not buy a Brit gun that was out of proof. For me, a sleeved gun would take a big hit........30-40% if the job was invisible and more if you could see a line.

I would have no problem with a gun that has just been touched up with re-blacked barrels or lightly refinished stock. I also have no problem in sending them off for a bend or a leather covered pad to fit. A way too short stock or an ugly extension would also probably disqualify it for me as I would not really want to get into a restocking job.