This is a very, very common occurrence. Since we got rid of title deeds and replaced them with the non-definitive Land Registry Title Plan, many, perhaps most, boundaries are actually shown as being in error to some degree.
The Land Registry Title Plan does not show the position of the legally defined boundaries, they are only defined by the fences on the ground when you buy the land or any topographic or boundary survey that may have been undertaken as a part of either gaining planning permission or defining the land for the purpose of sale.
In essence, it is up to the purchaser to accept that any title plan that forms a part of the deed of purchase is accurate before they purchase the land. Solicitors acting for the purchaser are supposed to send a copy of the plan that will form part of the deed of purchase and get their clients approval that it is right, which then puts the onus on checking back to the purchaser. It is always a very good idea to at least take a surveyors tape when looking at a plot and doing a rough check on dimensions, and better by far to pay £300 to £400 for a boundary survey before purchase to be sure that you know exactly what you are buying.
We looked seriously at two plots, and had both surveyed before exchange of contracts in order to confirm the boundary position.
On the first plot the boundary had been moved on one side by 14 metres, a public footpath had been relocated the same distance and the plot was essentially unable to be built on, as the remaining flat land area was too small, plus the footpath movements meant that the local authority started enforcement action the moment I asked them about it, having found the error. The estimated timescale for correcting the error was around 2 years, so we pulled out.
On our current plot there was a boundary error of about 5 metres in one corner, and the house as approved in the planning permission could not be built, as part of it would be on land owned by a neighbour. It took us a year before purchase to get two sets of Land Registry Titles corrected, new surveys accepted by all parties and an encumbrance on part of the land removed. From first making an offer to completion of purchase was 14 months.
Many people on this forum have had very similar experiences, in fact I think it's probably fairly normal for boundaries to be in error.
If you have bought the land as fenced, then you may well struggle to get back the 3 metres that have effectively been taken by the neighbour. It all hinges on whether there was a proper boundary or topographic survey done, and whether that survey formed the basis of your purchase. If you were just relying on an outline plan used for planning or similar, then the chances are that you don't have any recourse with regard to getting back that 3 metres.
Worth talking to your solicitor, but I very strongly suspect that the solicitor may wriggle out of it by saying that you agreed that the land you were buying was that shown on a plan, and that the plan you agreed to may not have been based on a survey or even have been correctly scaled.
Edited by jsharris, 03 March 2016 - 01:10 PM.