Fair enough if the car is genuinely unfixable. I do think you need to accept though that past choices mean that you cannot, RIGHT NOW, afford the car that would be ideal, and go from there. It's the dangerous thinking of credit and you're just on the tipping point of things getting much worse if you take on £9K more of debt.
Can I ask how much money do people tend to aim to have stashed away for a rainy day?
I think it helps to think differently.
What is a "rainy day"? Are you saving for boiler repairs, needing a new fridge freezer or washing machine unexpectedly, for having cash on hand to take advantage of a bargain by paying up front? Or are you saving for job loss etc.?
Name what 'known unknowns' could occur and start with that as a figure - say £1,000?
Then pay off all your debt as soon as you can.
Then start saving 3-6 months' worth of expenses in case of job loss.
At the same time you need to be actively saving towards bigger things you know you need - house repairs, new cars etc.
You will find your monthly disposable income is much, much less than you think it is and you will feel poorer...
...but you will grow much richer and have much less stress when you can just deal with the problem of a car that's on its last legs without juggling hundreds of scenarios of different financing options.