Hello, I am a solicitor with 20 years experience. I will try to help you with this.
Thank you I haven't slept for over a week with the worry of it all.
The short answer is yes but in a qualified way. The basic position is that you probably have a claim to the land on your side of the fence even if it was put in the wrong place through adverse possession (ie squatter's rights). The law changed in October 2013 but your 12 years adverse possession would have expired before then. I need to check the transitional provision of the Land Registration Act 2002 to see how the law works in your case. The basic position is that firstly your neighbour will need to show some legal basis for his assertion about the fence line and even if he does you very likely have a good claim to the land on your side of the fence.
I won't be able to check those provisions until quite late this evening I am afraid
Thank you. They say they are only bothered because don't want any problems if either of us decide to sell. We personally think problem is because the fence goes at an odd angle and fencer can't be asked. Look forward to hearing from you.