Hi there,
With regards to the BSA Super Meteor, I would say that you are looking at £70 - £90 range for a really good one. A lot sell on here at around £55-£65, but they often are in average/well used condition. Obviously at the end of the day it is worth as much as someone wants to pay, so if you were buying it and you thought it was worth £120 to you, then £120 is the price. Any similar gun new is going to be at least £170 or so, so £120 is a bargain.......
Hope that helps
Lakey