Hello, I am a solicitor with 20 years experience. I will try to answer this question.
Your description of the arrangement is a little unclear but it sounds as though your neighbours may have an easement granting them a right of way over your drive to access their garages. When you purchased your property your solicitor should have advised you about this. If you still have these documents (especially anything like a solicitor's report on propertylyou shoudl look at this as it will contain the information you are after. Easements are usually set out in the title deeds held at the land registry and you can carry out searches on line to see if this is the case. https://www.gov.uk/get-information-about-property-and-land/copies-of-deeds
As far as the property at the rear you describe is there anything in writing to sat it is yours?
There is a plan which says the entire area within a red line is part of the freehold of the property, this includes the whole drive area including the space behind my house. Would an Easement normally include the right to park on the property or just give access to the garage?
I have downloaded the land registry documents but there is no mention of the rules for the drive is that not the full deeds?
Easements usually appear on the title register. When did you purchase the property? Do you still have the documents from when you did move in? If not you may have to contact your old solicitors who should have kept the details.