Id say the tanker version is quite a rarity. All the tankers during my time were Fodens and then AWD's. I was in the heavy transport troop in Cyprus and had a fleet of mostly MJ's a TK and some more modern Bedfords used for UNHCR runs into the north. We had many variants of the MJ including GS, Fridge Bodied, UBRE, Water Tanker and of course the UGGI Wagons which were the sewage suckers! I had the honour/privalige of driving these. I did all the different jobs but my main ask was keeping the UN's cesspits emptied and dumping the load (no pun intended!!) over a cliff at a refuse tip outside of Famagusta. Best run was to an Austrian OP which was situated in the heart of the ghost city of Famagusta..very spooky!
Sorry for going off topic. Ill put my sandbag back now!
Anyway i love the Millys and would one day love to have a shot at driving one.