Correct!
@SewMumSew do not attempt to negotiate this debt. Any attempts to do so will be seen as you undertaking responsibility and that will land you in a world of trouble.
Report it to the police and get a crime number.
Write to the companies concerned and advise them of the crime number. Do not phone as any calls will be recorded and you may inadvertently say something that sounds guilty.
Contact the HA re:tenancy and get him out, if you can. If the police arrest him and/or charge him, because it’s a crime against you, the HA should be willing to take his name off the tenancy.
Freeze any bank accounts you had prior to you finding out about this fraud, do not close them, as this could be seen as an admission of guilt.
Open a new account, in a different group, and do not tell anyone that may tell him. So if you’re with Lloyd’s, open a NatWest account, etc. (Midland bank was always very good and seemed ethical, in as much as a bank can be ethical and remain open and solvent, so if they’re still around, maybe open an account with them).
Tell the DWP that you are now single and ensure you’re claiming all that a single person is entitled to. (It used to be the DHSS that dealt with unemployment, I assume you have a UB40? And then I think DHSS changed to DWP, but I haven’t lived in the UK for some years and I haven’t claimed benefits, except child benefit and that was years ago, so you would know better what they’re called, but just make sure you get your entitlements because even if he refuses to leave, you can be legally separated for the purposes of claiming, whilst living in the same house).
You have been given some good sites to visit so make sure you get financial advice asap and get records of your credit file, as there may be debts that you don’t know about yet!
Having your identity stolen is very stressful, and it is so much worse when it’s someone who is supposed to look after you and nurture you. Please do make an appointment and go to see a counsellor. Please do not underestimate the toll that this kind of betrayal takes on someone, not only emotionally but mentally, and psychologically as well.