Northeast

ESR (near Cullercoats) 

supplying components and accessories, and became the first component supplier in the North East of England dedicated to supplying the Entertainment Industry.Velmann kits and Cebek electronic modules

http://www.esr.co.uk/

Maplin

http://www.maplin.co.uk Arduino, rpi, makey makey general electronics 

RS Trade Counter Gateshead

Dukesway West,
Team Valley Trading Estate,
Gateshead, Tyne & Wear, 
NE11 0PN

Tel: 0191 491 0900 Email: rs-newcastle@rswww.com Our newly refurbished and expanded counter is now open. Come along and enjoy the new customer experience. Tweet and let us know what you think! Branch Opening Hours: Monday to Friday 7.30am - 4.30pm

United Kingdom

Robosavvy

Robotics & Makerbot printers
www.robosavvy.com

Oomlout

Arduino, components
www.oomlout.co.uk

Milford Instruments

 Ropbotics, Parallax, DMX
http://www.milinst.co.uk/

Bitsbox

Components, microcontroolers, all at a low flatfee of £1.50 postage per order.

Bitsbox.co.uk 

Cool Components

Arduino, robotics, radio comms, kits etc.

http://www.coolcomponents.co.uk/catalog/

Phenoptix

http://phenoptix.com arduino and pi breakouts leds etc free delivery over £5

Far East

Seeed Studio (China)

PCB Service, components etc.

http://www.seeedstudio.com/depot/

Wayjun (China) - Not the best website, payments by paypal, long lead times.

LEDs, in particular, very cheap super bright 5mm LEDS (http://www.wayjun.com/index.php?main_page=product_info&products_id=437)

http://www.wayjun.com/