building regs/planning house conversion

[deesmith27]

Apologies if this has been posted elsewhere.

I am buying three flats in a house in the Brighton area with the view to turning it into a maisonette and separate studio because we probably won't get planning to turn it into one house.

Every time my partner or I speak to the planning department or building regs we get told something different about what we do or do not need to submit. Was hoping someone here might be more knowledgable about it all?

Initially we only intend to do a light conversion - new kitchen downstairs and remove bathroom downstairs, maybe open up a couple of non-load bearing walls and take off a couple of doors to the shared hallway. First planning said we could do what we liked because it was inside. Then they said we should submit a certificate of lawful development application. Then they said it might be best to get some plans to go with the application. Then someone else said only submit lawful development application if we want to. 'WHICH IS IT?' I wanted to shout at them. Does anyone know?

With building regs, they seemed pretty laidback about the walls, but said we'd need to upgrade our energy efficiency which could cost us thousands as it's an old house and would mean applying for full planning as it's in a conservation area and we can't do anything including changing the windows without planning. Again, if anyone could give me a more sensible answer, would be very grateful.

Thanks
Dee x