http://www.webuyanycat.com/

Quickly is the key word!

Upload a photo of your cat and get an appraisal instantly!

Would shipping be included to the UK?

Not that I would go through with it, but this is a very interesting idea.  Hum.... I'll just upload a photo of Chip to see what she is worth.  (Just because I'm curious what a crabby-old-calico cat is worth.  I'm not going to sell her, honest....)