Well I've been paid by an ins co for fixing a leak! That one was an endfeed connection which had only been soldered round the end.They all specifically do NOT cover putting right the plumbing fault which causes the leak
Bit more on this one - it was a compression joint which had held 3 bar, on a new heating system. After running for about 4 weeks, the pipe jumped out. Couldn't have been done up much at all, because he "just pushed the pipe in and did it up", ie no new olive.
The suggestion of what's going to happen:
Plumber (whose fault/responsibility it was) will give customer a bill for £200 for fixing the leak in an "old water pipe". That'll cover the excess nicely. Then the ins co will be expected to pay for everything. Since the ins co are hardly going to take up floors looking for new bits of pipe, they'll probably get away with it