There's a postal address shown on that website (which is a legal requirement for a UK trader):
http://www.tessuti.co.uk/store/information.php
The email address on that page uses the same domain name (rather than Gmail, or similar, which is always a warning sign).
The phone numbers shown match those in the Phone Book:
http://tinyurl.com/37v6h29
The domain name is (as I'd expect from a bona fide trader) registered to the same address:
http://tinyurl.com/37z9qqz
The company is registered at the same address with Companies House, and all of its accounts are up to date:
http://tinyurl.com/3xubznm
The firm definitely exists at that address (although the web page indicates that the store has recently moved)
http://i54.tinypic.com/11w3s7c.jpg
A web search for 'review tessuti' doesn't throw up loads of horror stories. It simply finds a single excellent review:
http://www.reviewcentre.com/reviews257391.html
So it looks OK to me!
Chris