Rob, you could also consider asking as a condition of purchase, that they (Mosesgate) take the car to nearest Lexus dealer for them (Lexus) to inspect it and state whether they (Lexus) would be prepared to cover it with the Lexus warranty. I currently pay £1095 every 2 years.
If Lexus say,yes, you buy the car, if Lexus say no, you don`t.
Just a thought.