Thanks Janey. I did contact my local CP about a year ago when I was trying to catch a pregnant girl and they only used automatic ones then. I will contact them again and see if they have anything new now.
Although, saying that, major progress this evening! Gizmo, or should that be Houdini, sneaked into the trap this evening (first time he's ever gone near it, so I'm pleased), stole the KFC chicken that was tied to the roof of the trap, and then scarpered! He didn't even trigger the trap! Little sneaky wotsit!
I put the trap inside a large bin bag and then padlocked it to the fence to make sure that no-one could wander off with him. I also put up a poster with details of what I was doing, which seems to have kept nosy people at bay. It seems to have done the trick as this is the closest that I've ever been to trapping him.
I will try again tomorrow with tuna or mackerel - something that I can squish right into the far corner of the trap! I have a rescue place ready and waiting for him, so fingers crossed that I can get him soon.