It turned out that they hadn't took notice of either of the calls I made telling them I would pick the wheels up Friday am, and sold them on the Thursday. 
But...Once I had calmed down we enjoyed an open and frank exchange of views in which we agreed that it was their fault, that they would order me a new set, and throw in free fitting with free new locking wheels nuts.
So as I was calming down on the way back up the road it occurred to me that it's not the mistake that's the problem, it's how it's been dealt with. They have apologised and re-imbursed me for time/mileage by throwing in free fitting and wheel nuts, so now I'm a frustrated but relatively happy bunny!
