I have seen a few that I have been interested in but they always seem to be sold by the time I enquire, even if the adverts are barely a day old. Which makes me wonder a lot of the time if dealers really have these cars "for sale" or if they even exist. Sometimes I think they create fake adverts to generate lines of enquiry, tell you that vehicle is sold then they will try and sell you something that is real but they have had trouble shifting.
I have thought about buying on finance myself but it's just so expensive when compared to leasing a brand new vehicle. It costs me more a month to buy a £25,000 car on finance than it would to lease a brand new £60,000+ car.
I am not sure why GDPR would come into it; if you are purchasing something knowing that the person selling that thing has legal ownership of it would be classed as "relevant" and "adequate" information. Making that information transparent is a matter of legality and preventing unscrupulous people from commiting fraud. I work in data and have done for the past 10 years, so I have a pretty good understanding of GDPR.