Electricity debt from previous housemate transferred to me- please help!

Hey guys, not sure if this is the right place to post but I figure you guys may have some insight for me and may be able to help

I lived in my house with my previous housemate for 3 years, the electricity account was in his name and I paid 50% of the bills to his account, he paid the bill.

He has left the UK in January so we switched the account for the house from his name into mine, the electricity company told me there was £93 outstanding on the account, I owed him a hundred quid so no biggie, or so I thought

My first quarterly electricity bill came through in March, £1573, I was stunned. I rang the electricity company to find out how on earth I owed so much, they told me it was a balance carried forward from the previous year, when the account was in my previous housemates name, and that now the account is in my name the debt is mine.

I asked them for a payment history on the account, so I could see how we accrued so much debt, I assume he just stopped paying the bills. Problem is, they won't provide that because it violates data protection laws to disclose other people's payment history.

So now I'm in a situation where they say I owe this money, but can't provide any proof of the debt because of data protection, so I'm apparently to just accept the debt and they want to charge me £380 a month to clear it.

What do I do? I'm so stressed with the situation, I can't afford 380 a month, but can they pursue the debt if they can't provide a proof of it? can I refute the debt on these grounds in court? or am I just likely to end up with the 380 a month electricity bill plus court costs? I don't know what to do. Please help 🙏