Posted: 16/09/2013 at 16:09
Sorry, but injecting the walls is useless. Think about it. Is it really feasible that anything injected could do any good? The salesmen are very persuasive. They are apt to bring out moisture meters (designed for wood, not plaster) and talk technical. Most old stone builings do not have or need a damp-proof course. You have not got rising damp; you have penetrating damp.
The position must be relayed to the neighbour in writing, so he can study it at his leisure. If your wall can only be reached by going on his land he cannot deny you access. There have been court cases about this; he is in the wrong. You may have to arrange to do it by appoinment but he cannot deny you.
He is also causing damage to your property; again he is in the wrong. You would be quite within your rights to get a digger in and dig a ditch to keep your wall dry. He would not like that, so it is up to him to come to a mutually agreeable remedy with you.
I'm rather surprised that a full structural survey was so cheap - they are expensive things.