Owain wrote:
Bear in mind that *each* point on a lighting circuit must be considered
to be 100W or actual load if greater, with no diversity. The assumption
is that all the lights could be on at the same time. Max load on a 5/6A
lighting circuit is about 1200W or 12 points, so unless your circuit is
already very lightly loaded you will probably be non-compliant with the
Regs.

By "point" do you mean junction box (or rose on a loop-in system)?

It is lightly loaded. I have two circuits in an 900sqft two-bed flat.
The circuit in question currently carries about 600W tops (proably
nearer 400).

Antony