I have a detached garage / utility room. I'd like to have it converted into a self contained living area with a bed/living room, a kitchen and a bathroom. I have space to extend the length of the current building

It's single brick at the moment with a rubber skinned style roof (which would need replacing).

How possible is this?

Does it need planning permission because it's change of use. I guess it will need a second layer of brick so it can be insulated correctly, damp proof course maybe, new roof, electrics done properly, it has hot and cold water going to it at the moment. It's near the outside drainage.

So we are not looking to make changes to the actual house, just the garage.

Anyone done this, or do this sort of thing?