low voltage defo better than 240 v gu10 as much chrisper white light. led is defo gettin better but lamps are expensive if you want good light output. dont buy the £6 led lamps cause they are shit. only need fire rated caps for down lights with living accomodation above for building regs but we fit them as standard as better job with insulation etc. if you use these make sure you buy the heat down lamps or else you will burn the leads out over a period of time. Best way is labour and materials but will prob work out about £35-£40 per spot including materials. Dont buy that shit from screwfix