Update.
Well I went for the test drive in the is 250.
Brief thoughts: Overall I loved the car, with minor reservations.

Smaller than i had in my head from the initial look at an IS, but I can live with that. Not as much space in the rarely used rear seats, but fine. Gearbox feals nice and more responsive than my last auto. Paddle shift seems gimicky in this level of car............but i loved the clutchless changes!!

Handling seems nice in the time I had the car. Finish looks and feels superb! I want a Lexus.
Unfortunately, the only car they have is, I believe, over priced and have found two of the same age (within 2 months )and spec, 2k less and less milage!! This is a demo car and they may not have a margin in it, but come on! To top it all the bid on mine is the best part of 1k off "average" book price. The car is average at
very worst IMHO So i walked saying i will think it over.
I will give them a chance as the other cars are some distance away, but it's not just a few hundred quid!
I did not want to deal with AC as i had a horrendous time a number of years ago with them, and the less said about a friends nearly new Corsa .......the better, but i felt with Lexus I could be more relaxed in dealing with them. I hope I am still right. I know prices/trade in values are not the same as say hassle with them after buying, but the alarm bells are ringing.
I can however state that the sales staff are the best i have come accross in an AC dealership and have been superb and no complaints there. I may not from them because of prices, but it wont be because of the staff.
Cheers
Greig