You are unlikely to need PP because the structure is already there. The caveat is that because you are converting space where a car would normally go to something else, Planning may want to check that you can still park an adequate number of vehicles off-road. No harm in asking them.
You would need Building Regs approval if you are converting the space from non-habitable space to habitable space, but the uses you mention don't sound like habitable uses to me. Probably just as well because BR would demand that you insulate the structure to a high standard.