-
What do your insurers say?
What do the upstairs neighbors say?
Having pondered this a bit I am inclined to agree with @TW and @hoefla that upstairs should pay, but I did some googling (sound the armchair "expert" klaxon) and read that the neighbor would need to be proven negligent to be responsible.Worth checking what your insurance documents say.
Hope it gets sorted one way or the other.
Sounds annoying! I'd expect, rightly or wrongly, to cover the damage in my own flat with my own money (or insurance)