Regularisation - do it yourself or get a professional?



New Member
My main residence - complete rip out and rebuilt but no party walls involvement and only 1 structural addition of a mezzanine; all done properly with architects and structural engineers involved. It was surveyed the whole way through but I never got it signed off as there was one last bit left and we ran out of money. Of course this then was forgotten. The company doesn't exist anymore and paperwork cannot be found. I've spoke to the council and they've advised regularisation (renovation around 9 years ago). I've had a look at the forms and feel like I may be able to attempt it, I have architect's drawings etc. But have read some horror stories about issues after. Should I defer this to an architect instead to get the regularisation through? Or engage them only if I have any issues?
I want to do this just for the sake of knowing its done and dusted. Not selling and so not in a rush.
Any opinions/advice appreciated.