Mr Holdsworth has raised a good point . I remember some confusion reigning about the use of Fire rated downlights and to overcome the confusion , decided to only fit fire rated fittings by default. The heat developed by exposed GU10 50 watt lamps concerned me , we extracted some that were covered in old newspaper in the roof space . I think if they had been left on for say 2-3 hours a fire would have resulted.
Not fitted open back downlights for years .
I agree that a house is one fire compartment with the garage as a second compartment , but TBH always thought that the ceilings were 1/2 hour fire rated and drilling a row of 70mm holes destroyed that rating, hence the use of fire rated fittings.
I also note that most of the architect drawings we've worked to would state that :- WIring was to be to latest edition Regs..........smoke detector on each level ....downlights to be fire rated.