What's the cocking issue? If the piston slides ok but just doesn't latch it could be down to wear in the pivots/piston cocking link slot so the underlever hits the trigger guard, or it could be the trigger Sears and springs gunged/rusted preventing the sear engaging and or the trigger adjustment set too light. You don't say what Mark/year the gun is (serial number prefix will identify it)Google "date my BSA air rifle " and it'll take you to John Knibbs site.
Complete early airsporters are the nicest looking (especially the mk1) and in my opinion the nicer to shoot, despite having heavy triggers, not particularly accurate but good enough for tin cans/vermin up to 25/30 yards with practice, use Marksman 5.6mm pellets from John Knibbs, not the most accurate pellet in the world but in my experience they work a treat in old British guns .
A more modern second hand "premium" Springer would be a better bet over a budget new one, but that's just my opinion.