to be honest rescue is the way to go, the new owners are fully checked out and although we all might look like cats lovers we could be anyone and I'm sure you want whats best for her - when do you need her homed by?
I'm not techy so this may not work but...
http://www.haws-animals.org.uk/ this is Hounslow but they are very good
CATS PROTECTION - EALING & WEST LONDON
Registered Charity no: 203644
Support Shop: 3a Albert Terrace, Pittshanger Lane, Ealing, W5 1RL
Branch Tel: 020 8752 0793
RSPCA - SOUTHALL CATTERY
Rehoming Centre: Burket Close, Norwood Road, Norwood Green, Southall, Middlesex
Open: Every day 11am to noon and 1.30pm to 4.30pm (Closed Wednesday)
Shelter Tel: 0870 010 1846
good luck - I would hate to be in that position myself - please let us know how you get on if all else fails somebody may be able to help you in another way