Below is a list of retailers who are UKARA members as of July 2015, I make no comment on how good/bad they are!

Actionhobbies ltd – Titan Imports
Airsoft Quartermaster
Airsoft World Ltd Airsoft Zone Ltd
Ambush Adventures (Just Cause Airsoft)
Badger Tac
bbguns4less.co.uk
Bomb Up Airsoft Ltd
Bullseye Country Sport
CAMO
Contact Left Limited
Craftys Airsoft
Crawley Surplus Store
D and B Militaria
Elite Shooting Centre
EXTREMEBBGUNS
Firestorm
Firesupport Ltd
First and Only Retail
Frogmore Grange Limited T/A The Grange
GEAR OF WAR
Ironfoot Industries
JD Airsoft Ltd.
JUST BB GUNS
Land Warrior Airsoft
Marcruss Stores Army Dept
Military 1st (MMG Trading Ltd)
Milspec Solutions Ltd
Nightgear.co.uk
NTAC STORE
OPS-7 Airsoft
Outdoor Pursuits – Battletec International Ltd
Patrol Base Limited
Platoon Stores
Red 1 Airsoft Limited
RedWolf Airsoft (UK) Ltd
Rules of Engagment ( O I W STEELS )
Socom Tactical
Soldier Of Fortune Ltd
SPORTING SUPPLIES
Swindon Airsoft Supplies Ltd
Tactical Airsoft UK Ltd
TARGETSZONE
The Quartermaster Military Store
Top Gun Airsoft Supplies U.K. Ltd (Pro Airsoft)
TRIGGER HAPPY
UKBA Coventry International Hub
Wolf Armouries Ltd
Xsite Airsoft Limited
Zero One Airsoft Ltd.

The Component Shop – not airsoft per se, but great for batteries, chargers and connectors

A few global online retailers. Beware the perils of importing and customs! Do some research first…
Taiwan Guns
RSOV
Ebairsoft
Gunner Airsoft