If the 'Permitted Development' rights have been withdrawn, make an Planning application in the normal way to whichever Authority (Leeds?) deals with your district.
Removal of PD rights is a simple and effective way for the local authority to gain additional revenue via the planning fee.
This normally, only applies to new builds where plots are relatively small.
However bare in mind that once having applied you may not get the answer you would hope for, even on a shed.
Sheds used to be exempt
(outside planning legislation if they were under a certain size) Worth a phone call to the LA in the first instance.
