I am building a kitchen and lounge extension for a customer and have got to the 1st fix electrics stage.I would be happy to carry out this work after first informing building control but frankly do not have the time so got him to call a sparks.The electrical work consists of additions to the downstairs lighting circuit for the kitchen and lounge ,extension to a ring circuit for extra sockets in new lounge and extension to the original kitchen ring incorporating new sockets,FCUs and outlets for integrated appliances and a new 32 amp 6mm T&E radial supply to cooker switch and outlet for a 5.2KW oven.I suggested I meet the electrician so I could explain I intended to board & dab the walls and ask if he wanted any extra noggins in stud walls etc. SORRY to bore you with this long intro but now to the point.The customer about 5-6 years ago had anew consumer unit fitted a Wylex NH1104, all breakers, no RCD protection I suggested that possibly the cheapest way to have the new electrical works carried out and to conform to regs would be to replace the 32amp MCBs on the kitchen and lounge rings ( lounge has French doors so power may be taken outside) with RCBOs and use one of the 32 amp MCBs for the cooker radial.The electrician said that to part P certify, all circuits suppling socket outlets in the house would have to be RCD protected. I think this is wrong as I understand it to certify he only has to check main earthing is correct and that the circuits he is working on will take the additions and that his work is to 7671.One last thing the cooker radial is that OK to part P certify on an MCB not RCD protected.Please could qualified sparks give their comments many thanks