Thanks mate I'll have a look at thoseYou most likely need 13g, which is bigger than standard bicycles. the best keys are like this because they grip on 4 sides and don't slip:
http://www.ebay.co.uk/itm/Quality-Topeak-Duo-Bike-Cycle-Spoke-Key-Wrench-2-Sizes-/111936470576?var=&hash=item1a0feefe30:m:mJ-Rt-5k1Muz5BNZA6z0rvg
these ones have all sizes, but they sometimes don't fit well, and they slip when your spokes are tight.
http://www.ebay.co.uk/itm/Spoke-Rim-Wrench-Nipple-Key-Adjuster-For-Bike-Bicycle-Repair-Fix-Tool-/262477694786?hash=item3d1ce3c742:g:-k0AAOSwepJXWkH7