I posted this the other day at £14.97, it's now come down to £9.97 and if you have one of the £5 vouchers then you can get one for under a fiver.
Handy for playing Wii Sports Resort.
It might not show up when you search on their sites, I found it via offeroftheday.co.uk
EDIT ***seems to have vanished from PC World but still showing at the address below for Currys***http://www.currys.co.uk/gbuk/nintendo-motionplus-accessory-for-wii-02907424-pdt.html?srcid=369&xtor=AL-1-[Awin]
Improve your gaming experience with the MotionPlus Accessory for the Nintendo Wii!
Every slight movement you make with the Nintendo Motion Plus is rendered in real-time on the screen, with precise tracking of your arm position and orientation. Easy to use, you simply attach the MotionPlus to the end of the Wii Remote and play!