Thanks all - I really appreciated your collective wisdom and advise and the guides. I did it - bought the 2011 Lexus IS Advance in the end over the SR (it still had the nail in the tyre after last year's MOT). The Advance has everything I wanted except for the paddle shifters but it wasn't a deal breaker. The car has 50k on it, but last year the previous owner paid 500 pounds for service that included change of spark plugs, oil change (synthetic 5/30 Longlife 3), new filters (air and pollen), new battery (Bosch with 4 year warranty), and break fluid change. And 2 years ago he spent 300 pounds to purchase GardX treatment for the car's interior and exterior to protect the paint and leather. So I figured with service done and the protection kit, its not a bad deal. I hope I made the right choice.
It was so much fun driving it home - quiet, refined, comfortable and the V6 has such smooth torque delivery. I don't think we will go back to German cars after this.
Now I am purchasing rubber floor mats, a rubber trunk mat, car seat protectors, and car seat kick mats - I need to preserve this car!
Cheers all!