In article .com,
writes:
In my extension most of the new rooms will be having the small lights
inset into the ceiling - but I don't know whether to do it with low
voltage lamps or use the mains powered small lamps (Wickes currently
are doing packs of 4 mains powered lamps for £13.99).
Can anybody tell me of the relative advantages/disadvantages of going
low voltage or mains voltage for this lighting?

They're both horribly inefficient at general lighting, and
won't meet the building regs requirements for lighting
energy efficiency if they apply to your extension (I can't
remember off-hand when they kick in on a building project).
You should also fit fireproof caps over them so fire can't
spread through the holes you make in the ceiling for them.

LV is cheaper to run in terms of efficiency and relamping
costs, and has a wider range of different spec lamps available.
Mains is cheaper at initial install time, but otherwise it's
generally a disadvantage.

I would strongly suggest you think about a better lighting
scheme altogether though. Using spotlights aimed at the floor
for general lighting normally results some combination of
very energy inefficient and rather poor room lighting.

--
Andrew Gabriel