A British site featuring a range of products, primarily switches and keycaps, but also a few keyboards.
Unikeys
A popular Chinese site offering an impressive variety of sought-after HMX switches, keycap sets, and a small selection of keyboards.
Other Shops to Check Out
r/MechanicalKeyboards
The Reddit channel dedicated to mechanical keyboards. It features everything from community posts and intricate builds to Group Buy updates and giveaways from manufacturers.
SwitchKeys
An Australian site offering a variety of products, including QK keyboards and parts, GMK keycap sets, and more.
CannonKeys
A long-standing and highly regarded manufacturer in the field (known for producing Bakeneko keyboards and popular PBT keycap sets). They offer a very wide range of products of all types, as well as group buys for many additional items.
ClickClack
An American site with a relatively small but curated selection of keycaps, switches, and keyboards, including up-to-date Group Buys.