btw boundary disputes can be mentally expensive. A neighbour of ours had a dispute over a 6ft x 6ft bit of land and it went to Court and ended up costing over £50k in fees between them (it was in the paper). If you're only talking a foot or so it's almost certainly not worth spending a lot in fees arguing about it.
Thank you TooYoung, that is really helpful. Eternal, yes we have spoken and there is no mistake. He's being such an arse and a bully it's going to be hard to let it slide even though that's probably the sensible thing to do.
No you need to speak to you solicitor initially to establish how well defined the boundaries are on both your and you neighbours titles. A copy if neighbours title can he obtained from the land register, not costly (I am in Scotland but same procedure I would think) and if it is clear fence is on your land solicitor can write to neighbours on your behalf. It may be required to draw up a plan of what you own if not clear but visitor first port of call.
LoveVintage is right. I'm a property lawyer in England and your first port of call should be a solicitor who will interpret both sets of deeds for you. You would only be likely to need a surveyor if the boundaries are unclear and need redrawing.
You need the law to intervene on your behalf (always assuming you are correct).
Copies of title deeds can be downloaded from the Land Registry portal for £6 a pop, to include the written description of your property plus a plan. Beware though, if it is a tiny piece of land, or even if it isn't actually, the Land Reg always say their plans are 'for illustrative purposes only', so desperate are they (and I don't blame them) to prevent themselves becoming embroiled in litigation.
Far better sometimes, are any relevant historical deeds with plans, that you or your mortgage co may have. These may have within them original drawings of boundaries etc. A good solicitor would write a forceful letter to neighbour telling him to back off or litigation would follow. It's ridiculously expensive to litigate these days, so a letter like that might do the trick.
Yes can get copies of the land titles very cheaply, but be warned they only show approximate boundaries. To know exactly where the line should be you will need to consult the detailed plans (if any) that are attached to the house deeds.
The legal route is tricky because unless you want to take him on a long and expensive journey through courts then he can just say "No I disagree" to any evidence or letter. If he's determined to be awkward he can just keep on being awkward and cost you 1000s without him needing to spend more than a few pounds.
I know 2 people who went through a legal battle with boundaries recently.
One was a case of a bully who accused the person of moving the fence with no evidence. This went to court. The friend had 1st class evidence, including original house plans of the neighbourhood, the evidence of the agent who sold it and walked past it on the way to work for 25+years, the evidence of the original owner, a survey of the boundary which included the original greenhouse footings. The complainant had the land registry map, which actually supported the case against him, and several pointless, irrelevant arguments which were all clearly negated with supporting evidence. This cost nearly £20,0000 (due to the behaviour of the complainant who did not have legal representation and the necessity of using a barrister) and about £11,000 was recovered in costs (awarded costs - 10%, not all of which was paid and not all of it could be claimed for). It was sadly necessary but incredibly stressful.
Another was approached through the land registry when the neighbour disputed their records, went through their procedure, had the boundary surveyed. Decided the cost of legal action over the land (worth £70) was a waste of time and spent some of the money on a new fence on the boundary and making good the edge of the large pond which now abutted the boundary, and sold up. It was a big garden, so the loss would not be noticed by the new owners.
I would also add that in a very clear cut case, as you seem to be saying this is, a solicitor might offer you a fixed fee for half an hour's advice which might include writing a letter to your neighbour giving him seven days (for example) to return the boundary to its correct state, and that letter could set out the evidence you have, and give neighbour a bleak breakdown of the costs he would face if you took him to court. Might be worth a shot. I have certainly done tons of shirty legal letters in the past for existing clients who have had these sorts of issues. A typical cost might be anything from £70-100 plus vat depending on how much time they spend on it.
Actually, come to think of it, I've done loads of £0-25 'letter before action' type missives too. (Not been called for in a while). These are no nonsense and short! Usually done as a bit of a favour for a client, and where I simply do a paragraph or two telling the other side to pull their head out of their proverbial, legally speaking.