Seems that the enterprising soul was on holiday that week, I do have the 3/8" original studs!xvivalve wrote:If an enterprising soul had upgraded your studs to 7/16" you would have far more options on sourcing the nuts as they are readily available second hand!

You are of course right, the later studs were fitted for good reason, but I must admit to finding no cheaper sets of the 7/16" nuts either, mind you that's not saying a lot, as I haven't even remotely scratched the surface of the list of sources and knowledge gained over many years of ownership by so many on here.
Heard back from Chris Witor today, he's going to put them up on his site next week and he's looking for £4.20 each in black steel.