Ok I've just removed the end of one of my grips and theres an insert inside the handlebar which make it too narrow for the mounting kit that come with the Acerbis Handguards.
I went with a pair of Acerbis Rally II in the end which just arrived today so I might try fitting them tomorrow. Thanks for the replies!!
http://www.acerbistore.it/product.aspx?ID=289&C=155&L=2