I purchased a car without knowing it had unpaid finance on it (despite dealership's hpi check confirming as clear). Now an asset recovery service is threatening to repossess my vehicle. What are my next steps?

I bought a used car (3 years old) from a reputable dealership in August and paid outright for it. The dealership is a large, independent company that has very good reviews and has been around for 40+ years. They claim to have carried out all checks on the car, as they do with all their vehicles.

I've just been contacted by an asset recovery firm who have said that unfortunately, I purchased the car that has unpaid finance on it and so I have essentially bought someone else's debt. After speaking to the asset recovery firm, they asked me to contact the dealership and ask if they carried out an HPI check, which they had (and I remember seeing this on the dealership's website before purchasing the car but I wanted to double check). The dealership also sent me a copy of their HPI check (from a company called motorcheck, and one from AutoTraders own checking service), so I have two documents that claim there is no unpaid finance on the car.

However, I have since paid for an HPI check through the official HPI website, hpi.co.uk, and it came up with a red flag saying that there is an unpaid loan through Zopa Loans. Zopa has outsourced their loan to this asset recovery service, who are now threatening to repossess my vehicle, despite me paying outright for it and with good faith that there was no further cost on the car, along with the confirmation in writing, that there was no finance owed on it.

The asset recovery service then asked me to contact Zopa Loans, and provided me with a reference number (that matched the reference number from the HPI check I carried out myself). Zopa Loans have said that they cannot discuss this loan with me as it isn't under my name but the original loanee has cancelled their direct debit, which is why they've outsourced the loan. The asset recovery service have said that as I'm the legal owner of the vehicle, I am now responsible for this loan.

Where do I stand with this, legally? Do I owe the sum of the loan to Zopa or the asset recovery service? Can they legally repossess my vehicle despite me not knowing about this loan when I purchased the car?

I have read that the Hire Purchase Act (1964) SHOULD cover me, as it states that if I don't have knowledge of the finance, I am covered by something known as 'good title', which allows me to keep the car, but I have no idea of how to proceed, and which one out of the Loans company, the asset recovery service or the dealership will help me get out of this mess.

I appreciate any advice on this matter.

TLDR: I have bought a car that had claimed to have HPI checks carried out on it. I bought the car in good faith from a dealership, who also believed there was no finance payments tied in with the vehicle based on their checks. An asset recovery service has been in touch saying that I have bought the unpaid loan and they may repossess my vehicle.

Edit: from the auto mod post, I'm based in England if that makes any difference

Edit 2: Thank you for all the helpful advice, you've all helped me to feel a lot less stressed about it! It sounds like I should be able to prove relatively easily that I bought the car in good faith and so hopefully it gets cleared up quickly. If it looks like it's going to be a long, drawn-out process, I'll return the car to the dealership and get a refund as I've only had it for 2 months.