If your house needs major works doing, then it is highly likely you will require a major works licence for which you will require the services of an architect.
So, why not save yourself a lot of hassle and employ an architect now, get them to prepare the schedule of works and specification and ask them to go out to tender to builders on your behalf?
There is to be no alteration to the size or shape of the house.
Only internal work. Like a working toilet and stuff. 😯
Plus the raising of floors and dampproofing of walls.
Most builders obtain the licences anyway from what I hear. 😕