Mike Jenvey, We have probably met in the distant past, I was a Fairy on 50 Sqn from 1979 to it's demise in 1984, and although the HDU was a bit of a bodge job, at least it removed the age old Fairy problem of Water/Glycol running down your arm and up the sleeve when the hoses refused to lock on first time.
As to Start up, at least on the Vulcan we could stand in the dry, and if the AEO was a good'un he would start the rover and warm us up and dry us out.