What do you think of this garden fencing situation?

[Jippers]

My neighbour had a 4ft old fence. I wanted privacy, so I installed a 6ft trellis independently, along the same fence line. Effectively the boundary was double-fenced. Over the years both our respective fence planting mingled together. They then had a new garden built and all new fencing. I knew nothing about this until the day it happened. I came home from work to find a brand new fence but all my trellis had been ripped out & disposed of. What is left of my planting is severely damaged. The new fence is good quality and built in the right place, so I have no issues with that. I'm just pissed that they ripped out all my trellis & binned it. Neither the garden contractor or the home owner is willing to offer any recompense. I don't want to fall out with my neighbours but I feel hurt that they did this. They said they came round to knock on the day & tell me the two fences were inextricably intertwined but got no reply (I was out at work), so they went ahead anyway. Aibu to be upset?

No. I love my plants, that would leave me in tears 💐

Not really - they'd known for plenty of time that the fencing was going so they should have given you a warning that there could be a problem well ahead of "knock once, she's not in so carry on chaps".

Bill them for new trellis and new plants - send an invoice for the new trellis and send them a formal letter to say they have caused criminal damage to your property inside your boundary with no notice or prior agreement.
also include the costs to install etc and keep a copy of the letter and give them 30 days to pay

I do understand you being upset (so you’re not unreasonable) however if you are happy with the new fence, then you would not need to put up a new trellis so why would you want or expect to be compensated?
It is disappointing about the plants but it seems like it was unavoidable. And that your neighbour hadn’t told you in advance as the intention was simply to replace their own fence, they didn’t know until the day that your plants/trellis had become interlinked.