This is a simple list of UK things - fangroups, convention series, apas, and so on.
It is woefully incomplete.
It particularly does NOT include any group or institution which is primarly electronic.

If you would like to add anything - just a topic name, not full information! - send it in.

AARDVARK FANDOM

ANDROMEDA BOOKSHOP

ASTROSOC (Sheffield University) possibly 1st University group

AUSTRAL LEUGUE

BAD GROUP

BIG POND FUND

BRITISH FANTASY SOCIETY

BRITISH SF ASSOCIATION

BSFA

CAMBRIDGE UNIVERSITY

CHELTENHAM CIRCLE

COSMIC CIRCLE

DUFF

EASTERCON

FANCON

FANTAST MEDWAY

FANTASY CENTER

FEAPA

FRIENDS IN SPACE

GANNETS

GUFF

JUNIOR FANATICS

KITTENFANDOM - Kingston SF group

LAKELAND SF SOCIETY

LiG - LIVERPOOL GROUP

LONDON CIRCLE

MAD GRUOP

NESFIG

NOVA AWARD

NOVACON

OMPA

OPERATION FANTAST

OXFORD UNIVERSITY

PADS

RATFANDOM

ROMPA

RUBICON

SF CLUB OF LONDON

SEFF

SILICON

SOUTH HANTS SF

TAFF

YSFRG - Young Science Fiction Readers Group (aka The Youngfen)