Paul,
I got the wheel spacers from this shop in Reading called Gasoline Alley, but I think they're available from most places and I've also seen them in Halfords.
The only problem I have is that they're 6mm and I don't think it makes that much of a difference to the look of the car - they'd need to be 60mm before you'd notice it! I don't know yet what difference they'll make to the handling.
They cost me £12 per pair.
Andrew