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One thing I'd suggest on a practical note is to think hard about anything that you think could help facilitate or prevent your access being impinged upon, then getting that put in place before.
For e.g. (in France) my parents' place has a right of access over a 2m section of road belonging to the neighbours. In retaliation for a perceived slight they put up a gate which now makes it harder to enter (ironically leaving cars running outside their house for longer).
If my folks had put in a proper wall and decent gate before hand, it wouldn't prevent the neighbours from doing the same thing, but it would have been much harder politically to put a gate in front of their gate.
I'd also question why, in what looks like a straight forward scenario there you wouldn't ask the people with the access root to sell it before purchase.
Rights and easements are a common part of land registry titles.
In our Mews we have both rights over land not owned by us, in order to get into the mews in the first place, and we have easements which mean we have to grant access to the other garage and house owners/renters so they can access their properties.
It's not that straightforward sometimes, and a good solicitor can uncover some fun stuff.
We own the mews on a separate title and formed a company to do so in order that we could grant rights and parts of the property from the mews to our house title, to make any future sale easier. It turned out that some of those rights and easements were not written correctly and should have failed to pass down to subsequent owners, only nobody noticed. It also transpired that we had no legal right of access from our courtyard to a private road next to it, despite a gate having been there since the 1850s. A cheap indemnity policy was all that was required to secure that right in perpetuity, though I am not sure what it does if we need to claim.
All this stemmed from a huge property with many houses and stables being split up over many years into separate titles. Old houses can be fun.