A UK-based website offering KKB keycap sets and others, switches from various brands, a range of accessories, and a very limited selection of keyboards.
Other Shops to Check Out
KPRepublic
A popular Chinese website (they also have a store on AliExpress) with a variety of products
Monaco keys
A German website offering keyboards from brands like QK, Keychron, and others, keycaps (with a focus on German layouts), HMX keycaps and other brands, as well as a variety of accessories.
Nouvolo
A Hong Kong-based website offering a selection of Chinese keyboards (including relatively well-known brands like Weikav), alongside keycaps, macro pads, and accessories. The site also features PC cases and cooling solutions.
Eloquentclicks
A Spanish site offering switches, keycaps, and various keyboards, including models manufactured by the company itself.