Aibu to ask my neighbours to sort out their weeds damaging my fence?

[Bonden]

my fence fell down about four years ago in the wind - it was old and here when I bought the house. I apologised to the neighbours affected - all good.
i paid for and installed immediately a lovely new fence.
neighbours have abandoned the end of their garden which backs on to mine, and over the years brambles and ivy have grown up and are now pushing through the fence slats and footings. Not only do I not want to see ivy etc on my side of the fence, I also don’t want the fence to get nackered too quickly.

so AIBU to ask them to do something about the overgrowth?

You can ask, but they can ignore you. Trim the growth at your side

Napalm? Would they even notice?

I agree with the pp: you can ask but whether they do anything is another matter.
I have a similar problem with my neighbours next door. They have virtually abandoned their back garden - apart from dumping rubbish in it. And up until August the bind weed, brambles, buttercups, wild grass and docks were all pushing through the slats of the fence. I didn't ask them to do anything about it because they are scary people. But after multiple complaints to the council - it's a council house- the council workers came out and totally cleared all the weeds. Now the stuff is all growing back again though!
I really sympathise with you OP.
I love my garden and it's my hobby. But the problems stemming from the jungle next door make my gardening so much harder. And the dividing fence probably won't last another winter and I dread to think what will happen when it comes down.