You have always had to tread carefully when bidding on vehicles with D/A. Over the years we had weeded out the 'dodgy' dealers masquerading as 'main dealers' , these 'dodgy' dealers, if you searched them, were selling similar cars [age, screen price, makes & models] as ourselves. It goes without saying that the cars they were selling therefore were most likely 'lemons'.
Indeed, we learnt of one 'main dealer' in the Suffolk area, who were selling cars on dealer auction, via a separate used car dealer and earning a drink.
We learnt, sadly after buying, of another well known, established main dealer in the Kent area who had tried and failed to sell a part-ex of their own stand alone used car site, then failed to sell it from a live auction, before selling it of the D/A site [the car was a 'lemon']
At the end of the day, don't consider buying from anyone retailing cars which are similar to those you deal in, there's usually a reason they are selling their stock on D/A and those reasons are not always kosher !!
The D/A site wasn't policed that well previously with regard to the sellers being only main dealers, under the present D/A regime, please do your homework gents and be selective on who you are actually buying from, you'll find that some main dealers selling on D/A are nothing of the kind, it's no good being wise after the event, as we had learnt to our expense...