I can't see why not. It's not a 'change of use' as far as planning law is concerned and Royal Mail will deliver to anywhere that there's a mailbox.
You might need to check with the local council though as to whether you could use it as your address on the electoral roll (which, as well as voting rights, could have implications for things like obtaining credit or getting online retailers to accept it as a verifiable address for deliveries).
Your bank might also not be too happy if they found that you'd got no permanent address but there's no reason why you should actually tell them that there's no house at your new postal address.