oh dear!! if you go into the vets and let them know you would like to keep treatment minimal and don't need all the bells and whistles they might not push loads of stuff on you so much. sometimes they do this because you are new and want you to be aware of all the treatments available. i wouldn't take this as them not looking after your pet they may still be good vets. if you're still unsure shop round, i'm not from Leeds so i can't offer any advice there but i'm sure there is someone on here that could. As for the cat flap they have some on the market that have magnets in them. I personally prefer the CatMate ones with the electromagnetic. the lock on it is not as easy to force open as the Petmate and Staywell, but i do use the smaller Staywell magnet as the Catmate one is huge!! lol as for the odd behaviour i don't know your cat and it sounds like you might need to have the cat examined by a vet to be sure she's ok. you can also sprinkle a little bit of her used litter around the perimeter of the house outside to mark her territory with the other cats. this might put them off coming in to investigate.