Which circuit to which RCD?

[Grumps]

I've got a two RCD CU. One RCD supplies a recently installed and re-wired kitchen (ring, hob, lights). The other RCD is for the rest of the house ring and lights (a single ring for both floors, and a single circuit for all of the lights). The rest of the house is having a re-wire; ground floor ring, first floor ring, ground floor lights, first floor lights, smokes (interlinked). Where is it sensible to put these new circuits? Both rings on a single RCD or put one on the kitchen RCD? Same for lights; I presume it is more sensible to put the 1st floor lights on the kitchen RCD, and the ground floor lights on the other RCD. Ta.

[Tricky Dicky]

The usual way is not to have the same floor ring and lighting circuit on the same RCD, that way if one trips then some power can be restored to the affected zone be it ring or lights.

Richard