The CU is some distance from the kitchen and, needless to say, hidden in
an under-stairs cupboard. In any case is it acceptible to have the MCB
as the only way of isolating the kitchen appliances, especially the
hood? If it is it might be easier to show SWMBO how to test the RCD
which is separate from the CU and thus more accessible!

No ! it is not and the Hood will need to be fused down via a 3AMP switched
fused spur, now that you have said that the appliances will be built in they
are classed as fixed for the regs and MUST have a means of isolation next to
the appliance that is double pole.

Peter