I want to draw up an agreement with my neighbour to share

I want to draw up an agreement with my neighbour to share his driveway. However a small part of the driveway will be on property we own and I have just found out that it is unregistered. I really dont want him to know that and we certainly claim it is ours as we have had it for over 25 years when we bought the land. In turn the neighbour has a new house and has his eletric, water and telephone coming over my land. Would we draw up agreements each with plans and register them with Land Registry? Would i be forced to tell my neighbour that our land is unregistered? He isnt an easy person to talk with
JA: What steps have you taken so far? Have you prepared or filed any paperwork?
Customer: No, I just read the guidance on the Gov Uk website pw62 and understand that we need to fill in HM Land Registry form AP1. Do I need a solicitor to do all this. It is very important to us
JA: Have you talked to a lawyer about this?
Customer: Not yet. We have registered our house/property with Land Registry but not the shared driveway as this was agreed recently.
JA: Is there anything else the Lawyer should know before I connect you? Rest assured that they'll be able to help you.
Customer: The unregistered land is critical to us as it is part of our access but we only found out about it being unregistered when we built on part of our garden and built a smaller house for ourselves. The neighbour had a piece of land going back decades and he gave it to his son. His son wants a shared driveway and we agreed it would be practical and esthetically better. However, he does not know that part of our land which would be our driveway if we did not reach agreement for a shared driveway is actually not registered although it has been part of our fenced off garden for over 27 years