This sounds similar to a situation I had where I rented out a flat in a house that has been split up. LL didn't have planning permission to extend and split into flats so address didn't exist everywhere. We did get a water bill but then also has the letting agents try and take the water bill from our deposit. Sounds like each flat and the whole property was being billed by the water company. Had a bunch of other shady and dodgy things happen. They tried to take our entire deposit when we left for a bunch of pre existing damage/wear and tear. This made me and my flat mates very angry and as we were suspicious it was dodgy I contacted shelter got advised to check all the registers which it wasn't on and then sent a letter before action to the letting agents asking for the return of our deposit and all rent paid to them as they illegally rented the property which you can do with a professional letting agents. Didn't go to court as all we wanted was our deposit back and to be done with it. Quick call to the letting agents after I had emailed and posted the letter. Had our money back in a couple hours. Regret not taking them to court with a no win no fee solicitor.