Molly has gone back to her old family I'm afraid. She was collected by her owner's mum with a chance of being homed with an elderly lady with no cat at the moment. I think this is a better option for Molly and Posh, both.
Molly had this terrified look on her all the time she was here, I sensed she wasn't happy being a second cat, so best thing really.
Maybe Posh is meant to be an only child
Although, Molly came to me quickly and without much chance for me to prepare the ground etc for a new cat. It was a spur of the moment decision and I regret my rashness.
Elaine, she wasn't a formal rescue, more friend of a friend business, some thing else which was regrettable as I'm sure if i'd gone to CP I'd have been better advised. But thank you all for your help. I did try out your tips.