£20,000 inheritance while in debt

A few years ago my grandparents died resulting in a £20,000 inheritance, it sat in my mums account for a year or 2 as I was in university at the time and would have spent irresponsibly.

My goal for this money is to put it towards a house, my partner and I have been talking about the idea of buying but not for a while. I currently don’t have any help to buy isa or lisa set up (although that would be the next step)

Through uni and after I’ve managed to rack up a decent amount of overdraft debt (about £4,000) this wasn’t an issue as the accounts had 0% interest as they were student/graduate accounts, but they now are charging interest.

I’m starting to take control of my spending and putting money away for our kitten and saving to get out of debt.

What would be the best thing to do with this money, isa for the house, get out of debt, invest? Just looking for some other opinions and advice, thanks in advance :)