conifers and stuff

Can I run an issue by you all? It’s a garden/boundary thing. Well, two boundary things.
When we moved into our house some years ago, the neighbour over the back fence had a single huge conifer in their back garden. It was already taller than their house and blocks all the light from the back of their next door neighbours house and garden. That really wasn’t our business at the time, but events move on.
The fence that divides their garden and ours belongs to them and has never been never painted or maintained on their side since it was installed. It is a good quality fence with substantial concrete supports and posts. With their permission, we have painted our side and after a couple of storms, have repaired parts of the fence, again with their permission. The neighbours didn’t want to bother repairing it themselves.
So far, no problem. We want to be good neighbours, live and let live etc. But this past summer, the neighbours have had a lot of work done to their garden which includes a border just on the other side of the fence. In that border, they have planted several trees (not conifers). This is the first issue.
The trees are right up to the fence, already touching the fence, with no gap between fence and tree. One of the faster growing trees has lifted a section of the concrete supports nearby causing damage to their fence. As the others catch up, I’m sure other parts of the supports will be affected. As trees don’t pay attention to boundaries, there will be significant overhang of branches, branches pushing against the fence, together with an underground network of roots
Which leads to the next issue. Their huge conifer, now the height of two houses has thrown out underground roots that have this year, noticeably spread under part of our garden and disturbed a small retaining wall on our side causing a crack in the bricks and mortar.
The neighbours seem oblivious to the damage that such large trees in suburban gardens can do, we are not hopeful that they will bother too much about any damage to fences bearing in mind they have not maintained it so far. And we not hopeful that they will appreciate the extent of overhanging branches, unwanted root systems on our side. But we are very concerned about the rest of our retaining wall and a patio area just beyond. Also the destruction of the boundary fence and the fact that if we put up a fence on our own side, that too will be damaged as the trees mature.
Doing the Google thing, it seems that massive neighbour disputes can arise from simple things and particularly boundary issues, and we certainly don’t want to fall out with them. But equally, in a few years time we will be dealing with a number of very large trees right up to our border with significant overhang and an invasive root system, together with increasing damage caused by the conifer. We would like to “nip it all in the bud” before the problems are overwhelming.
So what is your advice here? How would you approach a tricky neighbour problem?