Neighbour boundary advice please

[Neighbourisssues]

We have lived i house for nearly 10 years.

6 years ago neighbour put up fence to replace hedges. We suspected on our side by mah e 6 inches but ignored. Course to one year ago, neighbour had external. Built that we think encroached on our land by a further 6 jnches. DH against falling out with them. I think are taking the piss:

I have been routing around old pics, can clearly show extension is in our side.

google is confusing, can anyone the timelines for me to disbute the above?

Had external what built? An extension?

did they remove the fence that was already 6inches on your land and then build something a further 6 inches?

you can’t let this go. You need to look at land registry and see a lawyer

you aren’t past any timelines for disputing the first action and of course the second as it’s just happened.

if they removed the fence and encroached then they know exactly what they are doing. It won’t be you causing a fall out. It’s them