Cookson Gold - Everything (almost) for the jewellery maker, often do free UK postage if you buy online
Walsh - Good quality jewellery tools
Bellore - Friendly! Silver chain and findings, gemstone beads, some tools...
Rashbel - Silver chain and findings, gemstone beads, some tools... (slightly different stock to Bellore)
Holts Gems - Fine gemstones
Wards - Gemstones from basic to amazing
Just Castings - Plating and lost wax casting
Gleave & Co - Watch and clock materials, some jewellery tools
Rio Grande - US based - mind blowing choice of tools, beads and findings (and great customer service!)
Kernowcraft - UK based. Gemstones, metal clay, tools, books - fast shipping
Palmers Metals - UK based. Sheet metal, findings, chain and Swarovski beads
CJ Resins - Clare John teaches resin courses and sells all the relevant supplies
Metal Clay Ltd. - UK based. All things metal clay - good customer service and fast postage!
ABS Metals - UK based ebay store - good deals on copper and brass sheet, fast postage!
Vitrum Signum - UK based. Enamelling equipment - kilns, enamels, tools