thank you. In the context of a sale, to the extent you can keep this matter on an informal basis the better as if it becomes any form of formal dispute, you will have to declare it to any potential buyer. however, to the extent you are not able to prevent the matter escalating into a formal dispute, if there is uncertainty with regards ***** ***** location of your actual boundary the first thing to look at is your title plan which from what you say you have already done. Occasionally, though not often, measurements can appear on the plan but from what you say this is no exception in that measurements are absent from the plan which will be expressed to be for the purpose of identification only.
In these circumstances the plan is, whilst drawn to scale, only for the purpose of identification and will not necessarily establish the exact location of the boundary line very precisely. Where this is the case you can either agree between you where the boundary line lies or failing which you would need to resolve the matter either using the RICS boundary resolution service or through the land Registry adjudicator or alternatively the County Court.
It can often be difficult to determine the exact position of a boundary in terms of centimeters or inches but a plan should enable identification of land in terms of several feet usually. As above, properties are generally registered with a plan for identification purposes showing the general position of a boundary. Sometimes it can be relatively straightforward to determine the location of the boundary by reference to another structure such as the house but not always and even then not necessarily with the degree of accuracy that may be required.
If you are unable to agree the location of the boundary line, one of the most cost-effective approaches as mentioned above is that you can ask the Land Registry to determine the boundary on the title plans by instructing a surveyor to prepare a very precise plan showing the exact line of the boundary in the surveyors opinion. You will need to use a RICS qualified surveyor to draw up a plan. You then complete form DB (link below) and send to the Land Registry who will inspect the same and serve a notice on your neighbour offering him the opportunity to object to your proposals.
There is a fee of £90.
from there, there is a process that is followed whereby the neighbour will have the opportunity to either agree the proposal or reject it and prepare their own report to counter yours. The land registrar will then make a decision and if either of you disagree, that decision can be appealed to the property tribunal.
However, irrespective of the outcome of the above process, because from what you say the fence has been in place for more than 10 years, there would be a basis on which the claim adverse possession of any land which is determined in the above process to actually belong to your neighbours on the grounds that the fence has been in place for more than 10 years, and therefore your parents have had factual occupation and possession of the land in the honest if mistaken belief that it belonged to them. Accordingly, there is really no point in the neighbours pursuing a formal dispute as irrespective of the outcome, I cannot see that they would be successful in being able to claim the land on this basis