I recently shot my mates BSA Standard, I'm unsure what version it was but really enjoyed it. I'm now thinking of buying one to add to my very modern collection of air rifles, and to hopefully try out a bit of vintage airgun shooting at my local club.
Is there much difference between the versions? And what should I be looking for in terms of condition, common problems and power? And what should I be paying for one in good condition (just to give me a ballpark idea).

Any help would be appreciated as I'm planning to go to Kempton arms fair and hopefully pick one up.