What do you get from a dealer?
I ask this as although you get a bit more legal protection...you can still do everything and more to be sure the car is what you want.
ie....
Get an RAC/AA check done 160
(sounds a lot but well worth the money as it is also insured and the top check is way better than the basic check most garages do)
Check the history, if need be call the garage and ask details.
Is vehicle still under warantee.
I bought private, saved about 1500 on the going lexus garage rate. (also did all of the above, and was happy with the deal i got)
I also went round a few lexus places looking and at one i saw them resprying an area of a lexus round the back.....kinda made me wonder what you DO get for the extra dosh?
At the end of the day, if there is something you dont like...walk away and look for another.