Local clubs that I've either shot at, or are part of the Middlesex County Archery Association, or otherwise recommended

Greenwood Osterley Archers (GOA) - I feel I landed on my feet when I found this place! Only 10 minutes from home, and a great club

Aquarius Archers - Finchley

Cranford - Hounslow

Laleham - Staines

Spelthorne - Feltham

Royal Richmond - Richmond

Guildford - Guildford, Surrey

Windsor Forest - Windsor

Woking - Woking

London Archers - Kensington

Saints & Sinners - This site has a great handicap calculator, very useful!

Mayflower Archers - This site has a very comprehensive tournaments diary