Leak into neighbours flat...

[ahdguy]

Hi,

My frikin bathroom has a leak on the sink waste pipe, and this has made the downstairs flat ceiling get damp in one corner and they've come to see me looks like their ensuite ceiling needs new drylining...

Whats the usual thing, do I get them to get some quotes and stump up? Or will my insurance cover it (or theirs) now I have fixed it?