Tony,
Just for infomation the land registry information confirmed that my neighbour had indeed 'pinched' some land!
This opened up a whole wolrd of pain that might be useful for others to hear about in case something similar happens.
Here goes:
The neighbour (kind man that he is) was claiming that he had been using and maintaining this tiny strip of land for over 12 years, therefore it was now rightfully his. This seemingly blatant cliam was likely to be upheld in court I discovered to my shock.
He thought he had the trump cards at this point - I've since discovered that he has been coveting the garage for some years, which explains a lot.
However, because the work I needed doing was critical to the stability and future value and integrity of my house we were allowed access and the work has been completed. A guy form the Mark Group actually advised me that this was a line I should stick to. This was far more useful thatn the legal advice I was getting!
Anyway, I can assure you that the builders we used left as much mess as possible in the neighbours garden

. They got extra cups of tea for that one......