Re:
although i can build wheels at my shop and i have built deep section aero wheels before i don't have a specific Mavic account which is needed in this case to get that rim, but i would suggest Gary at GA cycles in Southampton as i know he has an account with them and he is an excellent wheel builder.
he even builds motorbike wheels, some of which have done the IOM TT in the retro class, he knows his onions and not too far from you
mention me, Jon of Jon's Bike Repair, his shop number is 02380 636648