Thanks for the feedback -
To clarify a little :
Doesn't matter if auto button is on or off, or if high, med or low is set for the fan speed, it's as if it's defaulting to low fan speed. The temp of the air that is coming out is hot.
Works appropriately when it's warm and the AC is operating with the fan speed slowing up or down as you would expect as the temp in the car changes.
Over the years I've noticed that the fan slows a bit when you come to a standstill and are at idle and then will speed up as the gas is depressed to start, which I have assumed is normal. In the present case however, it seems to be at the point of just starting to accellerate that instead of the fan speeding up again it just goes to low speed and will stay there only to resume the appropriate fan speed when I again come to a stop.
Again thanks