YANBU. For a successful long term relationship, you both need to be on the same page in all aspects. Financially, you're not. It's entirely up to you whether it's a deal breaker/red line.
It probably would be for me. But I'd need to know what the two £15k loans were for. I'd also be thinking whether his car finance was a necessity, i.e. for an affordable/realistic car, or whether he was constantly leasing a "billy big bollocks" car to make himself look big! I'd basically be re-evaluating his entire personality/attitude/etc.
If the two loans were for "genuine" reasons, i.e. necessary home improvements required upon buying his home AND his car was a realistic/average one, then maybe I'd be able to work with it, but I'd also want to satisfy myself that when he'd paid off the loans, he wasn't just going to splurge again, getting into more debt etc. Likewise, I'd want to satisfy myself he didn't have other debt, i.e. credit cards he wasn't paying off in full every month, etc.
I absolutely abhor debt. It can ruin your life. Fair enough when it's absolutely essential, i.e. a mortgage or a loan for a new roof for your house or a new boiler, etc., but I couldn't be involved with someone who gets into debt for things that aren't necessary, i.e. holidays, a car beyond their needs, hobbies, etc.
Yes, I've had "debts", mainly our mortgage which we paid off in full after five years, and a couple of times we've had zero percent car finance, (but we had the money to buy outright, so we could pay off the loan immediately had we wanted to, but stupid not to benefit from zero percent interest whilst earning interest ourselves!), and once when I was on the bones of my arse earning a pittance and trying to finance my own accountancy studies, I put some study books on my credit card knowing I couldn't pay it off in full, so I paid half and the rest the following month, incurring a few pounds interest which I really, really hated, but it was a necessity and well controlled. The only time I'd ever not paid my credit card in full.
Luckily (well not really as I wouldn't have chosen him otherwise), my DH was exactly the same, so we were on the same page from the day we met. He never had any debt either, in good control of his money, etc. My previous only serious boyfriend was the opposite, and it really changed my opinion of him as soon as I found out, so we only lasted a few weeks - he had loads of maxed out credit cards and store cards, paying off the minimum only every month, and spending like there was no tomorrow buying rounds of drinks for people he didn't know, throwing clothes away rather than washing them, he was "into" photography and must have had a dozen cameras, etc. Just sheer spending with no thought about the debt he was wracking up nor how he'd ever pay it down.
My elder brother was the same, drowning in debt with nothing to show for it, and I think that's why I am the way I am. He'd leave his card statements, bank loan statements, etc lying around and I could see the interest and charges being added and it almost made me sick. Likewise he had barely nothing tangible to show for it, but loved the attention of constantly changing his cars, designer clothes, throwing money at his latest hobby so he had the biggest/best at whatever club/society he'd joined. It was all attention seeking. Sad really. He's retired now, still in enormous debt, living in a tiny squalid house that is in a terrible state, lived his life just robbing Peter to pay Paul to service his card debts, loans, overdraft, etc., all despite having a well paid career. Literally nothing to show for it. He'll have paid tens, if not hundreds of thousands in interest and debt charges, and all he has is a house full of old junk, dozens of electronic keyboards, dozens of computers, (all covered in dust), half a dozen clapped out old cars in his drive and front garden. So, so, sad, all because he couldn't control nor manage himself financially.