It's possible you could get this charger for £7.50 if you query the half price offer online by phoning your order through Argos Direct (0845 640 2020).
The deal says half price charger when you buy a motion plus controller but the system seems to apply the half price to the original £24.99 price. As the charger is showing as £14.99 (that's £10 of original price) I suggested to the sales staff that the 50% off should be applied to the £14.99 making it £7.50. They agreed, so I got it for this lower price
They were also able to apply the free delivery code. Missed out on quidco though.
The controller is a few pounds more than the best on the net but you are getting a motion plus duel charger at £7.50!
You might be lucky if you challenge. Not promising anything though!