Yes, it had occurred to me to go straight to an IS F. Unfortunately they seem to be holding their value extremely well. Even 2008 examples are fetching upwards of £22,000. But then they did cost around £50,000 to buy. Unlike the IS 350 which had a retail value in Japan of around £24,000 when new. The problem seems to be the import duties and agents fees.
Actually, I had to do a 30 mile round trip this afternoon involving both motorway and country B roads. And I rediscovered how really fast the 250 is, with excellent roadholding, effortless motorway cruising and very impressive acceleration with the transmission in manual, the power button on and maximum revs used. The only disappointing aspect is the lifeless steering, but you can make allowances for that.