Bats in the belfry, windows are jammed - London flat renting, deposits & landlords

Our kitchen ceiling roof was leaking this morning. There is a flat on top of ours which must also be damp.

Last time this happened - about 6 months ago - I spoke to the family in the flat above us. The water had come through the roof and into the childrens bedroom. When I asked them who their landlord was they couldn't/wouldn't tell me. I then called my landlord to find out if they knew the owner of the freehold (I figured that's who would have to repair the roof). They said they didn't. Could that even be possible?

I then called up the real estate who was previously managing our flat before the landlord decided to cut them out and manage the flat herself. Again, they said they didn't know the owner of freehold either.

Straight after that first leak, the family upstairs moved out. Literally within a day or two, dumping all their water logged stuff in the front garden including soiled nappies and other filth (another story). Some quick repairs were made to the upstairs flat and a new family moved in.

Now there is a leak again and I expect the whole thing to repeat.

Is my landlord lying? Surely they must know who the freehold owner is. Why won't any of the families who have lived upstairs tell me who there landlord is?

Besides moving out, what should we do? I feel bad for the families who move in upstairs and then get their possessions destroyed by rain because the roof hasn't been repaired.