Need help please RE; Student Accom missing landlord

Hey Guys need some help please.

We have been students renting a house since September but we're unsure about who our landlord is. We were originally renting off a woman but all the times we met her she was always under the influence and one of us had to practically carry her up the stairs. When we moved in the house was in a complete state, whole in the ceiling, you could literally sit on the toilet and see into the kitchen, there was some much rubbish in the back garden and the place was just absolutely disgusting. That landlord went missing and we got another one who is a friend of the man who owns the house. There is a leak in our ceiling ongoing since September, still not fixed. Mould in several places, one of the cabinets fell off the wall a few weeks ago and the heating went the other week so we where all freezing for the week. We all had to sleep in the sitting room, 5 of us to keep warm. We just discovered he is not even registered our tenancy, we have never met him, have no contact number or address. He is avoiding people who have repaired the house and they are contacting us looking to get him. We've all been sick since we've been here.

Have we got a case for the PRTB?

Would appreciate any help/advice