Yes I agree with BeenBeta the cost can spiral. However, its our home & business so we cant move away (sorry cant say too much).
You can get away with lots especially inside. Obviously you cant knock down stuff - pretty obvious.
So far we spent £100K and recently the builders were here for another stint - wouldnt be surprised £20K. Still not live-able!
The house was damp and over the years far too much patching up had been done to poor consequences. We stripped it all back to the stonework and the builder repointed and replastered. The ceilings were pulled down and loads of floor patching up done.
My experience is to do as much as possibe without involving the planners. Conservation planners really dont live in the real world and I have argued my case successfully many a time. Work can be held back for months. Beleive me any atime I wanted to set fire to the place just to get rid of it because after a few years you fall out of love with it. Living in a smelly caravan for a couple of years can also send you over the edge.
I'm lucky that I come from a architectual background so I can draw and understand technical bumff.
Always go with a builder with lime/old building experience most modern builders havent a clue. Hence this costs.