For all interested parties re: Brake calipers
Had same problem with my 2001 46,000 mile IS
It's a lot more aggressive than wheel balancing !
(checked hub/disc temp, but be careful, one will be much hotter than the other)
Sourced locally, and coming in at £73 each :)
From EK Brakes (they do post items out too)
And I had to get both calipers, approx a month apart though !!!
(so beware of the problem Martin, as the other side will be in a similar condition)
Brakes work well, and happy it's all fixed now