You've focussed on electrics and planning but if you've been knocking through walls are you sure that there was no planning required there and are you sure that the council won't pull you up on the insulation regs.
From my experience council building control tend to sub out the electrical part of the sign off - they just want the cert from the electrician.
From my experience council building control tend to sub out the electrical part of the sign off - they just want the cert from the electrician.