Hi,
I trained as an electrician many many years ago but the job i do now means i haven't had any current training. the original question asked about installing DIN rail units near a CCU. i assume that we realise that the only cables in a CCU are the main lighting feeds, and Ring Circuit feeds, there is no way to control individual lights from a CU or a position near a CU.
if you want to control individual room lighting you would need to fit the DIN rail unit at the location of the light, you would also need to install a switch to overide it unless you intend leaving every light in the house on.
the DIN rail unit has exposed terminals so it really needs to be fitted inside an enclosure, personally i wouldn't screw the DIN rail to bare wood then clip modules onto it i would bung it in a plastic enclosure.
I don't think there is a problem with you doing the work under the new regulations providing you don't make the final connection. Get it tested by a professional who can then make the final connection.
having just taken a quick look at the unit it has an input for a local switch, as the unit needs to have a live and neutral in order to function it would have to be fitted at the lamp, if you wanted to fit these locally at the CCU you would need to wire two two core cables to the room, one dropping off at the switch the other running up to the light fitting. this will cost a bomb to do as you would need to run two two core cables to every room.
i'm not sure what the current trend is amongst sparks when wiring houses these days but if it is done using junction boxes there won't be a live and neutral at the lamp just a switch line and neutral, with a live and switch line at the switch.
if it is done the three plate way by looping the live and neutral from ceiling rose to ceiling rose and dropping down to the switch then your going to have to fit the DIN module at the light fitting under the floor boards.
Regards
Mirv