Thanks both for quick reply..

I hadn't considered the MCBs being single pole

I like the idea of a Grid switch, but hadn't considered feeding each DP
switch from a single MCB.

Can the Grid Switch be out of sight, in the pantry? or does it have to
be nearby the appliance?

The building Regs were applied for / passed 4 years ago, and this is
the last job on the extension (apart from the bathroom happening in
parrallel). I understood that as I had started the extension Part P
didn't apply?

regards

Adrian