There were two blokes in the Lidl car park today selling (and installing) wiper blades... 
... a polite, "fuck off" sent them on their way... 
Did you check to make sure yours hadn't mysteriously vanished before they tried selling you a set... 
How much were they asking, they are silly prices here and the local motor factor only stock them singly? 
He was speaking in forrin so I'm not sure...

There were other people having them fitted tho but I suspect that quality of the things was about as good as the quality of the watches and perfumes that they try to flog you in car parks here...
Best thing is to buy the rubber blade itself in long strips or rolls and just replace that part...
Like this...