Think of putting our own fence up close to our neighbours fence – for privacy, thoughts?

So, me and my partner (both women) moved into our new house 6 months ago. At first our new neighbours seemed super friendly but nothing too weird. They’re both retired, husband and wife in their 60’s ish. We’re on the end of a terrace so only one neighbour.

We immediately noticed the wife seemed to lack some boundaries, she would invite herself in and just chat on forever. Hints don’t work. You really have to basically tell her to leave, or, if she catches you outside, literally just walk away while ending the conversation over your shoulder. He seemed alright out of the two at first.

But then he starts really pressuring us to cut down a large tree in our garden, saying it’s roots will probably damage both our houses and the drains. We agree because it’s also casting quite a large shadow into both our gardens (ours in the morning, theirs in the evening). I sort of mentioned the tree gives us both privacy, as the fence separating our gardens is 4.5ft and placing a trellis on top would be nice… He initially agrees, we cut it down, and lo and behold now it’s his fence, we can’t touch HIS fence (title deeds say it’s nobody’s fence). We’ve brought up the pack of privacy a few times and he says words to the effect of “pity this is my fence”.

He also like his seems to lack boundaries, sticking his head over into the garden to initiate conversation, looking in when we’re sat outside minding our own business, and it’s making us both uncomfortable to be honest.

This is why we’re thinking of going nuclear. Our own 6.5ft fence just on our side of the boundary line. Has anyone actually done this and what happened? Also given they’re not our favourite people, vastly older than us (30’s Vs 60’s) we don’t care if they start blanking us.