So having initially looked at a house I found that everything was in good order and the seller seem genuine in respect everything being able to answer my question and to provide the relevant documents if requested.
Having gone back home and reviewed the listing, I noticed that the neighbours extended wall comes past the boundary and covers the potential house's side entrance (back end leading to the garden). So essentially...when you look at the side entrance from the front of the house, it doesn't reach the back entrance of the garden... You just see the neighbours brick wall... So the side entrance only to leads to a side door only (which the seller has currently blocked - 'as they don't use the side entrance').
I've been told that boundary lines stated on the land registry website (UK) doesn't specially specify boundaries but I fully suspect that either the neighbour has built on the other side after making a payment or they've just built it and risked it... Current sellers have been in the property for 12 years.
Any advice please?