Hi all, my Audi dealer has confirmed to me that this is an issue with the tyres. I was sceptical at first but they met me early morning with a technician and the manager of the dealership and we tested it thoroughly, doing turns in the cold and looking at it from the outside too. They concluded that the tyres make that noise when cold and on hard lock left or right, forward or reverse and it's a characteristic of the tyres and not a fault.It's been up on the hoist and the tyres rotated front and rear with no difference. I've had the car 15 months now and no problems otherwise so I'm going to stop worrying aboiut it and try and get some Avon ZZs when the time comes.
Thanks guys
Panos