I have a 1999 1.8 Freelander which I am very happy with. However, recently it has developed a strange noise. It only affects the car after it has been driven for 10 minutes or more (ie when the fluids have warmed up). It is a speed-related squeaking noise. It starts at around 20mph and rises in frequency with the road speed. Putting the car into neutral or changing gear makes no difference to the noise. As I slow down the noise stops once I get below 5mph.

The noise is most noticeable outside the car - ie when you have the windows open. With the windows shut, it is hardly noticeable.

The car has 60k miles on the clock and has been regularly serviced by a LR agent.

Any ideas?