A few years ago all they had to do at LHR was turn up with a dispenser and do what the
BA refueller told them to. These guys were paid more than the BA refueller signing for the job. Now they have to do it all. BA have introduced nice tolerences to accomodate the imperfect refuel. In the old days it would be an arm wrestling contest with the E.O. that a stick check was called for because they were (on paper) a bucketful short. The bean counters won this one big time!
I would imagine that a HGV is only required if you have to drive a proper bowser. The usual dispenser is the sort of base vehicle that doesn't need a HGV. It is possible that HGV is required to prove that you have a modicum of common sense and an understanding of the word responsibility. To be fair, most of the guys and gals I meet are good guys and gals until there is a problem or it's their last job of the day.