First - welcome to YT, There is really no such thing as a "teacup" Yorkie
Before buying a puppy read this:
http://www.yorkietalk.com/forums/fea...ead-first.html
Also, I see you are in England so check out the Kennel Club site
The home for dog owners and those working with dogs - The Kennel Club
Click on the Buying a Dog button and click on Find A Puppy service. And look for a registered Yorkshire Terrier breeder in your area.