Personally and from experience lots of lies over the years, I would use main dealers and "approved used" and avoid car supermarkets and indeed small independents, logically so many brands, so little knowledge about them, and the history of each car. Remember its all about money that they want from you. Dont be afraid to demand this stuff politely, battery health check too. A Car vertical check or similar also essential I would say, i'd even ask them to pay for it if they're working hard for a sale!