Cheers bruce thanks for your time.
I cannot remember how thick the heat shield material is on the IS200, and I'm too lazy to go in the garage and have a look, but the IS250 material for the shields is thin, cracks easily and makes a horrible rattle. It may be that it's cracked rather than a loose fixing, in which case it will need replacing.
Thanks got replaced today.Nice quite car again.Thanks for your help Tango.