Hi Seb, I wish I could help you with this one, the only thing I could find which is probably a mile away from what it is, a cloth badge with a wheel.
Wheeler, carriage & wagon repairer.
thank's for your help.
i found this bagde on "google"...
i think it's a mile away from what it is too...
Two of this helmet where found next to Caen, Normandy.
More on the lines of a "Rail Transport" unit. Possibly under RASC.