Thanks for the feedback guys, I have spoken with my local dealer and complained that this level of noise is totally unacceptable in a new car, particulary one costing this sort of money.
In fairness to them, they have agreed, in fact after I complained, they took another S4 out for a test which also had the conti's on and confirmed what I was talking about.
They are going to try and get me a change of tyres through Audi.
I will let you know the outcome.