fs thinking about it my nearest Dogs Trust when I lived in North Yorkshire let me foster a dog for 2 weeks one Christmas. Spoke to the manager and she was against it but then said Oh, we've got a little staff bitch who has been nearly breed to death and is gaga so she doesn't know where she is anyway so you could take her, and I did. She had been chucked into a shed when her puppy farm owner had finished with her as she was too old to breed anymore. I took her home and she walked round in circles until I but my hand out and stroked her head, then she stood stock still. I loved her for those 2/3 weeks, probably the first love she had ever experienced. She was doubly incontinent though! So the thing is they may make an exception for the right dog. Good luck, it's very rewarding.