If you're buying an older car, avoid European brands. Rather buy Japanese or Korean.

With an older car you have no warranty so there is no need to buy spares from the agents. The non agency spares shops stock a wide range of non-genuine parts for Japanese and Korean cars at good prices.

With European cars the demand is low so only the agents keep spares (at 3 times the price).

I have a Renault Clio and this has been my experience.