Used car outright or finance?

I used to be a big believer in Bangernomics but my faith is being seriously shaken. I’ve had the worst luck with my last three cars and it’s making me wonder if cars genuinely just hate me. My wallet is getting rinsed every month by mechanics.

So far had a

- 2009 Insignia 1.8 that lasted 18 months. Bought at 98,000 before the head gasket went at 120,000 miles.

- 2009 Ford Focus 1.8 that I bought at 80,000 miles. Replaced front suspension arms, wheel bearings, valve cover gasket, EGR, three engine mounts, before someone wrote it off weeks after the work was done

- my current car. A 2015 Astra GTC 1.4t that needed a new oil cooler and rocker cover gasket upon purchase. Rear main seal has gone and clutch is slipping so that’s more cash down the drain.

I’m quite mechanically minded and know how to fix/replace basics but I’m sick to my back teeth of owning a car that needs constant attention. How do you buy used cars that are relatively problem free? Or is it time to jack this all in and get a mortgage on wheels?

Interested to hear thoughts