after about 10k miles of overheating at any speed above 60mph,my car is now back to its former reliable self with 170 k on the clock. the fault was resolved by replacing cambelt & waterpump together,aprox 10k early but well worth it.total cost £470 inc parts,coolant vat & labour which seemed pretty good from a genuine audi dealer. hopefully I can now return to problem free motoring.thanx for all the advice you have all given me on this excellent forum site.