Well it seems that Curt actually sent me the wrong invoice in the first place . He replied earlier today asking when I'd paid for the accessory kit and that he'd sent me the invoice for something called the stocking stuffer... Rather irritating indeed...

EDIT: Righto, now that I've paid for the accessory kit, things should hopefully all fall into place once I get the refund for the Stocking Stuffer. Now I just got to wait... again .