Buying a car - suggestions?

I passed my test yesterday (yaayy!!) on my first attempt, with 3 minors. Grateful and happy for that.

So obviously as a next step, i’m looking to buy a used car. Facebook marketplace is a headache - all sellers trying to sell category cars overpriced - where they might’ve bought that for mere £ on auction. It is hard to find any private sellers (which I believe I can trust more)

I have inclination towards VW, BMW, Audi - ambitious, I know but still - a wish.

Do you have any recommendations for places I can buy a car from?