I have a technique that avoids a lot of that, I won't give the game away completely but lets just say I rely on the expertise of others.
I can't although I obviously do a full strength HPI check and ensure the seller doesn't have the log book shown in the advert. The way I look at private sellers, apart from those that aren't actually private sellers of course, is that if they have the time/patience/fortitude to advertise privately rather than shoving it on to WBAC/a n other then they are probably honest. Not many have the front to put a car up for sale knowing there's a huge bill looming, or that the car drives like a dog/smokes like a chimney. Generally people are reticent about face to face exposure with strangers and are worried they'll get scammed or ripped off somehow.
If someone has a car that has known issues or a big bill looming then they will try and palm it off on a trader or WBAC because they feel OK about tucking up a rich car trader or big firm like WBAC.
It's not always the case but I've bought 20 cars privately since the turn of the year, sold them all on and not had one screamer, apart from a bloke who moaned about the fuel consumption. Touch wood. I'm trying to get access to the good stock out there before people give up selling privately and just go to WBAC for a quiet life.
I struggle to buy at BCA because of the prices, like everyone but I'll have to expand my net father now, as I'm giving it a go full time.