Thanks Adam, the socket is the problem I cannot put it behind the washing machine because the wall wart that powers the driveway lights protrudes to far to allow the machine to go fully back.

I did consider putting it above the CU but the knockout in the case is smack on the meter below and although I have on order a fairly low profile gland I dare not risk lowering the CU.

In its planned position I estimate approx. 80mm gap to the underside of the worktop so no problem opening the front flap and that allows for a batten to be fixed to support the worktop as although the whole thing will be fronted with a base unit it will have to be foreshortened because of the gas meter etc.

There is a possibility of moving the socket to the right but from the position of the isolator the tails will end up across the socket unless I do some fancy bending round it.

Where you see the vertical slot in the plaster I have fitted a 50 × 50 trunking and all the cables coming from under the floor will be housed in it on that side of the CU is a single 32mm knockout which I do not think will cope with the number of cables which are 1 × 10mm2, 2 × 6mm2 and 4 × 2.5mm2 all T&E. The plan is to chip out a cavity behind the CU extending up to the trunking and feed all those cables plus the ones coming down the wall into the back of the CU. There are several 40mm knockouts and I am hoping 2/3 will suffice to feed all the cables into the CU. To preserve the integrity of the CU the plan is to flood the cavity and openings with either intumescent foam or sealant, I think sealant might be more controllable.

Before I fit the CU to the wall and remove any knockouts I will have a play on the bench with it and see how much of a mare the various options are and will report back before I do anything permanent on the CU.

Thanks to all for all the advice up to now!

Richard