Ok I just went and measured the rear span (distance from the inside edge of the rear forks where the rear axle goes between I presume), It is 126. I measured with a tape measure so if the tolerances for this are lower than +-2mm then I better do it again with a steel ruler to be sure.

So are 7spd wheels 126mm as well?

£200 was for both wheels, £65 x 2 for the rims the rest on labour. It may be I was being taken for a ride But then central london prices have a habit of being inflated.