Done a bit more digging and I would say up u need a 12mm Allen key in through the non drive side to remove the bolt.
http://www.edinburgh...ed-freehub-body
I can engage the bolt from either side Nick, should I rotate in a Clockwise manner if undoing from the non drive end ?
I read that they should be around 30Nm when fitting, so hopefully It will budge at some point.