Just want to reiterate - you could end up having a mortgage you can't pay, on a house you don't like, that's worth less than you paid for it.
A poor credit score due to lack of debt history would make for a higher interest rate, but this rate isn't just high, it's verging on sub-prime. Plus no credit history wouldn't bar people from a joint account - it would need to be a bad one, IMO. You are both on the electoral roll at your current address, yes? That's one of the simplest and easiest ways to improve your credit rating, because it proves that that person lives at that address, and a con-man isn't committing identify fraud. If you really do want to buy that is something that is well nigh essential. Perhaps also get a credit card, put something small but regular on it (a supermarket shop each month) and pay off in full. That improves your rating, too.
Please, please pull out. We've had people do it to us before, and while a pain it wasn't a big deal - we understood, it's the biggest investment decision they can make plus will be their home, they have to be certain. YOU have to be certain. So much might go wrong, it's going to cost you a bomb, and for what? You don't even like the place!
The rule of thumb is that a house costs you 1% of purchase price to maintain per year, and in my experience that's about right. Storm drains get clogged and need clearing, aerials get blown down in winds, tiles go on the roof and have to get sorted before leaks start to rot the joists, appliances go kaput, boilers need servicing to stop them going kaput, repainting and carpet cleaning needs to occur every few years and that adds up, God knows what else, just to stop the place falling to rack and ruin - you aren't improving it and adding value with any of that, just maintaining.
Enjoy your baby, and freedom from being the one who has to think about all this stuff, unless you fall madly in love with a house. The obsession with house ownership in this country is imo nothing short of madness, when it leads to people living somewhere they aren't mad about, and can't afford, and might destroy them financially, when living somewhere lovely is cheaper and financially safer.