Paul,
How about putting a dab of white Tippex (typewriter correction fluid) on the side of one of the sprocket teeth and another dab on the belt. Then run the car until you hear/feel the skipping. Then look to see whether the two white dabs of Tippex are still in line or have moved. That will prove whether the belt is skipping teeth or whether the issue has another cause.
Thanks Tony - nice idea... but I'm not aware that the belt circumference is an exact multiple of the sprocket circumference. Is the no of belt teeth an exact multiple of the no of socket teeth? If so it will work, otherwise it will not align...
