Possessory - Leasehold

Good Afternoon. I wonder if somebody could advise. The original deeds were missing and there's about 3 years left on the possessory. I want to sell the house (I have indemnity insurance) and part of the garden. But as a leasehold, until full deeds are through. In the meantime I want to keep part of the garden (Outline planning permission given) Can I do this? Thanks

Kitty - that's a Q for your legal rep and perhaps more importantly any buyer to answer. The key will be proving ownership and minimalising any perceived risks re the sale and what's included