Hi,
I have recently written an ebook with Don Clarke who ran a successful coffee shop for 15 years, with a half million pound turnover.
In his book Don advises that you really need to look for premises with seating for 60 in order to make it worthwhile financially. There is a website that lists catering busiensss, including coffee shops, which are up for sale:
http://www.ukbusinessesforsale.com
He also advises that money spent on an interior designer or a shopfitting company who may also provide a designer is worth its weight in gold, as a good interior design will attract customers. There is a website for the national association of shopfitters at:
http://www.shopfitters.org/pages/intro.html
Hope the above helps.
Regards
Tracey