[cameronh90]

I should have said that I meant common for recessed lighting.

They often use 12V MR16, inherited from the halogen days, and are pretty common in houses renovated from the 80s until the 2010s. The other option was GU10 which ran at mains voltage, but they were less common until LEDs became popular.

Recent new builds, flats especially, often just include hard wired fixtures without interchangeable bulbs at all. They often still have separate drivers above the ceiling, with the wiring to the lights being low voltage, but sold as a single unit. But I think that's just so they can make the light itself thinner...