Unfortunately at the time of writing I am unaware of any DVT support groups in the U.K however you may want to contact the following charities.
Lifeblood: The Thrombosis Charity
Registered Charity No: 1090540
Postal Address: The Centre for Haemostasis & Thrombosis, First Floor, North Wing, St. Thomas’ Hospital, Lambeth Palace Road, London, SE1 7EH
Tel: 020 7633 9937
The Circulation Foundation
Registered Charity No: 1102769.
Postal Address: The Vascular Society Office, Royal college of surgeons of England, 35-43 Lincoln's. Inn Fields, London WC2A 3PE