My friend and her DH just added a small en-suite to the corner of their attic bedroom. It's 2 partition walls, plumbing including a few external pipes for waste and a toilet/ sink and a shower cubicle.
It's finished and looks gorgeous. Now they are panicking they didn't get a building regs cert for it before they started and if they apply for one now somebody will come and drill into the finished work.
Do they even need one? Could they not bother with a council building regs cert and then get indemnity insurance for it when they want to sell instead?