There are many types of down lights the versions in this video
would work on nearly any plaster board, they are basic surface mounted, only hole required is for supply cable, there are many more versions, this is just the first I found.
The larger the lamp, the less are required, but lighting has never been easy. With low ceiling I see the point in down lights, nothing to hit your head on, but with the traditional MR16 versions you actually needed height to get spread. I used a 2D down light in a bedroom, really a mistake, fitted as given it, but down lights come in many sizes.
The problem with lighting is to work out how it will reflect, I fitted two GU10 wall pods in last house over the bed as reading lamps, when the ceiling light failed turned them up to reflect off white ceiling, and really surprised how two 6 watt lamps lit the room, but pointing down at bed seemed only just enough to read in bed with.
So lights pointing down to the floor need a light coloured floor to reflect and spread the light, or the light needs to cover a large area to start with. One foot square seems to work well, 2 inches or 16/8th of an inch, to my mind too small.
