You can start here:
http://www.nicindy.org/
The North-American Interfraternity Conference (NIC) is the umbrella organization for 71 American college national fraternities. Under "links" on the NIC's homepage you can access all member fraternity organizations national websites.
Check out the various national fraternity websites and look for ones that interest you and contact them. Let them know you are interested in starting a chapter of their fraternity in the UK.
Good Luck