Paul,
Going by the photo in the advert, it is definitely an RAF Coles, there has been one on here recently, a museum at an old RAF base in Wales, Millom (?) had one donated to them. Note the legs on the jib for doing a static lift, I think for lifting aircraft with undercart problems. Now the Army had AEC/ Coles bridging cranes, cab same as a Mk1 Militant, 11.3 engine and 4 cyl Perkins on top, they lifted 10 ton blocked at min radius.
I used to do the SWL tests and repairs on Army and RAF cranes of these types and later, so it is old memories coming back to me.