Surely this is not the AS-12 to which you refer.
http://www.wonderland.org.nz/Missile_Index/as12.htm
If so, it surely has no connection with the Cheviot Missile.
By the way, my friend has e-mailed the picture and the GPS location of the beast to Otterburn, so watch this space.
Depending on the existence and magnitude of any "reward" I reckon he owes us all a pint.