Regarding 'humane' traps: I was under the impression that was against the law to release vermin? What are you meant to do with the critter once you've caught it?
If it's a grey squirrel, you *could* apply for one of the 200 release licences issued each year and legally release it some months later after all the paperwork has been completed (by which time it would be quite fed up of the humane trap, I imagine). But otherwise, kill it.
Either with bullet/air-rifle pellet to the base of the skull, or the more complicated but fewer-legal-complications-of-gun-ownership method of a half brick: put a large plastic/hessian sack over the mouth of the trap, transfer the vermin to the sack, work the critter until its head is secured in a corner of the sack and apply half-brick forcibly to rear of head. Works every time. Wear gardening gloves to avaoid being bitten through the sack.
If you get a squirrel, hang it for a day before skinning - it's much easier then - and substitute it for rabbit in recipes. No-one ever notices the difference if you take the bones out before serving it.