Chess Associations

English Chess Federation (formerly the BCF) [1]
The International Chess Federation (FIDE) [2]
Braille Chess Association (British) [3]

Chess Leagues

Middlesex Chess League [4]
London Chess League [5]

Internet Chess

Chess Cube (promoted by the ECF) [6]
Free Internet Chess Server [7]
Internet Chess Club [8]

Chess Shops

British Chess Magazine Chess Shop [9]
The London Chess Center (Shop) [10]

UK Clubs

Hackney Chess Club [11]
Harrow Chess Club [12]
Streatham & Brixton Chess Club [13]

Other

Venues for away matches [13]
WLCC Web Server Statistics [14]

See chessgames.com [15] for a Masters games database (including Mark's games), kibitz [16]ing, a basic introduction to openings and daily puzzle.