He sorted me out OK.
My wheels are SD1 Vitesse, and he supplied:-
"In that case they will be #5001, 7/16" x 20 unf, dome top medium (length) mag sleeve nuts @ £2.00 each (inc washer) plus P & P. See website for full details & dimensions"
Be aware that on the web site, when he lists "steel" nuts and "alloy" nuts, he is referring to the wheel, not the nuts!
Jim.