Just put some in the bathrooms as I had access from above via the loft -
great.

Would also like some in the kitchen but cannot get access above as the
first floor is laid with ceramic tiles.

So I have a cunning plan;

Drill mounting holes for lights in kitchen celing.

From the existing central light point, create 12mm deep channels, about
15mm wide, to the mounting holes.

Then run narrow conduit to carry the connecting lighting cable along the
channels, tack to the joists to hold in place, and re-plaster over.

That way I need not worry about getting the cables across the joists
from above and, as I would only be cutting to the depth of the existing
plasterboard ceiling, I wouldn't run foul of any other wiring / pipes etc.

Does this sound feasible or am I about to contravene wiring regs ?
I presume the void between ceiling and floor above (the depth of the
joist) would be adequate for ventilation ?

Any other suggestions welcome.

PS the joist run perpendicular to the direction of the proposed lighting
cables, so "fishing" behind the ceiling is out.