As Cristo says, VAG (volkswagen audi group) owns vw, audi, seat and skoda so every single model of these manufacturer is a pick and mix of parts and engines based on either of the vw or audi chassis, just different bodies.
The used car market has changed hugely since Covid and bargains are a lot more difficult to come by, they are about but you really have to search, my Mercedes CLS recently chewed an auxillery belt that caused a catastrophic oil leak so had to bin it off. I had my criteria… Saloon, auto, cruise control, diesel and comfy and ended up in a 3ltr V6 Jaguar XF, I’m into my cars so wanted a decent looked after example with full service history and any remedial work carried out, I spent a solid week looking through auto trader, ebay and Facebook, car specific forums and Facebook groups and ended up with an absolute bargain from an old boy on an owners page on face book. The type that had spent thousands on maintenance.
Decide a budget and factor in you’ll pay either side of a couple of hundred quid of it, haggling isn’t really much of a thing any more and I find it quite uncomfortable doing it, having said that if it looks too good to be true it will be and don’t ever be afraid to walk away from something that is a piece of shit just because you need a car. The amount of times during my younger days I’ve walked into buying something that was nice and shiny on the outside but a piece of shit under the bonnet and ended up costing me a fortune to fix or maintain.
Once you’ve settled on what you want, owners forums are absolute gold mine of information, you get a feel for any common issues or niggles that come up and can find out if they’ve been fixed or not before you buy or if you’ll have to be the one that foots the bill.
As with anything, condition is alway key, I now never ever buy anything that hasn’t had a full service history with invoices and stamps to back it up, wouldn’t worry at all if it wasn’t a full dealer service history (dealers are just an excuse to charge more anyway) and then you can check the mot history via the government’s mot checker site and it’ll show you every mot the car has had, whether it’s passed or failed, any advisories and what it’s failed on, this is also a good tool for correlating mileage.
Lastly, something else I do, again once settled on a make and model, I youtube it, reviews, buying guides all of it because you get a good idea of what the car looks like inside and out so you know what to expect and again any common mechanical issues to look out for.