I think c is for chinese, at least these are the cheap ones going for £50 at amtech as Steve said, not imperial ones. I replaced the brushes on my original vac which had done 200 hours and now no problem with it. This vac has done less than that but pretty sure its the brushes, I wouldnt like to buy a new vac when it can be fixed for few pounds.
AJB do you think my vac uses same as Hi-Track motors?