Turned out all 3 were a bust. The two higher mileage cars just weren't up to scratch (one had serious electrical issues actually) and although the lower mileage car was nice the dealer wasn't budging on price and was a right prick into the bargain, so I walked away. After that I decided to give up on the Lexus and look at some other things.
Lo' and behold, I spot another car this morning - 07 plate with 80k miles at £7,500. Hot tailed it over first thing. Clearly done all of it's miles on the motorway given the number of stone chips and some dodgy door mouldings but it's got FLSH, one lady owner from new and the interior is immaculate. I doubt anyone has ever sat in the passenger seat. I pick it up on Wednesday. It won't cost a fortune to have the exterior touched up and get some new mouldings.
Funny how things work out!