A large range of 1/56 resin vehicles
http://www.agnminiatures.com/

Fantastic ranges of miniatures.
http://artizandesigns.com/

Bolt Action Miniatures are the WW2 specialists in 28mm
http://www.boltactionminiatures.co.uk

A very large choice of rules and minis
http://www.brigadegames.com/

Very nice WW2 1/56 vehicles for 28mm miniatures.
http://www.chieftainmodels.co.uk/

28mm Ancient, Dark Age & Early Medieval Figures
http://grippingbeast.com/

Perry Miniatures is the company run by the great sculptors Alan & Michael Perry.
http://www.perry-miniatures.com

The Wargames Command Post is a UK based retailer of a lot of range of miniatures and vehicles
http://thewcp.co.uk/

A large selection of ranges from Dark Ages to WW2
http://www.westwindproductions.co.uk/