Details from "The Green Machine" by Barry Hollis and John Thompson.
SXF 284 HL B4 HOFSTC Also used as a GP. At central motor auctions 3/89.
B4 indicates Bedford RL. HL indicates that it was used as a Hose Layer, but also used as a GP means General Purpose.
HOFSTC (also from Green Machine)
"Although not a fire brigade as such the Home Office Fire Service Technical Centres at Moreton in Marsh and Washington Hall, Lancs., had an extensive fleet made up into three mobile fire columns (MFC) in order to train full time, retained, AFS and other service personnel. The Centre's also trained RAF officers and men for the same purpose. The HOFSTC also had, in conjunction with the Territorial Army, the Army Home Defence Centre (AHDC), Devizes, to which a number of vehicles were attached."
So although the Auxiliary Fire Service, along with the Civil Defence Corps and Police Mobile Column, were under Home Office rather than MOD control the main operators were military personel. It makes it as "military" as a Green Goddess, but just how "military" that is, is debateable.