Owain Lastname wrote:

Peter Burke wrote:
Strict adherence to regs editions is not too important to me, just
doing a
good job in the spirit of regs.

I would allow lots of extra space for SPDs and AFDDs which are
suggested now and may be required in the future.

Fitting RCBOs now is good, you'll save 4 ways from the lack of dual
RCDs, you can choose to not bother with SPD, and nobody's likely to come
along and insist in retrofitting AFDDs in future.

If AFDD/RCBO in future are double-width you need 50% fill/ 50% free
which is quite an over-provision.
They're already available single module, bargain price.

https://www.screwfix.com/p/wylex-afdd/898jk

If you look at David Savery or John Ward's videos about how difficult it
is to get an arc to trip these things, especially on low current
circuits you wonder why they even make a 6A version?