Who is liable for the excess on this insurance claim?

I live in an apartment block; the apartment above me is rented out to a tenant by the owner.

A month or so ago, the tenant up stairs left a tap on for some 6 hours which caused severe flooding into my own home causing much damage.

I lodged a claim to the insurance company and now there is an excess, who pays the excess? I would imagine it is the owner of the flat whose tenant left the tap on? I ask because when I queried with the insurance assessor he said the excess is up to the “politics in the building” how odd?

Also they came to repair the air conditioner which was also faulted and it is half repaired as the display is not working properly so I cannot set it to a temperature for example. Do I tell the assessor this?

One more question why did the assessor choose a more expensive quote of his own, and not use my quote which was cheaper for the carpet for example?