At least you know what it is, now.... I'm puzzled at the tenant upstairs not wanting to call the landlord, that would surely be the first thing to do, after all, its the landlords problem, surely? Your insurance company may well want to be rather firm with him about needing the landlord information, as they may well be seeking recompense from him. If you suggest to him that your insurance company will need the landlord details (rather than you yourself being "awkward") he may understand the need for that involvement. After all, as well as him needing plumbing and flooring work, you'll be needing a compete new ceiling, and soem decoration and mould treatment work. And of course you may be allergic to the mopuld treatment, so you'll need to go into a 5 star hotel over Christmas...
Those adaptation plumbing types are very good, they always seem so, well, adaptable, and work out how to solve a problem. So good in fact, that one of our staff here is marrying said equivalent person.... We're on the local authority side, after the OT's have said what they want. Its not what I do (at the moment), but I can design adaptations, 'cos I is a designer by profession, innit?