Fence Building

ADJOLYN

Hi all, not sure if i'm in the right place but here goes, i live in the end of terrace, at the side is a passage 36 feet wide which is access for garages, the local council say this land is unadopted by them, the land registry say it isn't registered to this house but i have a copy of the building lease from 1914 which states that if the land wasn't adopted by the council 12 feet was to be maintained by the owner of my property not to be built on except for fencing, i would like to put up the said fence to create a driveway but as it isn't registered would this be legal, also in my land registry details from 2004 when i bought the property it says "please note the lease comprises also other land" the property did used to have a ground rent payable but neither the previous owner or myself have ever been asked to do so, if anyone has any advice i would be very grateful