Had to return this little girl to where she came from this morning, I checked her last night and she was full of milk. I had her in the vets this morning to double check that she had already given birth and she had. Fingers crossed her kittens will have survived the night and that she'll continue looking after them. I've asked the lady to continue feeding her and to try and find out where she goes, once we know we can get her again. Her kittens have only just been born according to the vets, possibly within the last 24/48 hours, fingers crossed it's not too late for them.