Spoke to @ShellStationsUK this morning. The Twitter thing is too much for them, so they gave me an 0880 number.
I spoke to a polite lady in Manila, who assured me she was trained in UK issues.
After my explanation, which she appeared to listen to and, from the keyboard noises, take some notes, I got the answer I was half expecting...
Health & Safety.
The rationale for the 'Company Policy' was that the AdBlue pumps for HGV's were designed to deliver at 40-litres-per-minute, which was too fast for cars, which should be used at 2.5lpm.
"OK, but the pumps have variable flow nozzles controlled by a trigger..."
"Yes but the pressure is too high."
"Not according to other users who have filled at different service stations with pumps."
"Can you name those stations."
"Err. I don't think so as you might just stop them letting other drivers use them"
The conversation was a lot longer than that. I pointed out that Shell was treating some customers unfairly, but this didn't get through the H&S script she was sticking to. The price difference is not justified and she did not try to defend that, merely stating that AdBlue Pumps for cars may be available in the future.
I asked for details of someone in the company with a responsibility for these marketing or H&S Decisions that I could perhaps contact over my concerns. This was declined as she stated "Data Protection prevents me from giving out those details."
(That from a customer services department based outside the UK/EU which, as they failed to get my permission to process my personal details outside the EU in a country that is not recognised as having sufficient protection - whole other issue there!) Anyway, I have asked if they could get someone to contact me.
Meanwhile, I have done some research and conclude that there may be issues raised under Competition Law as you cannot treat customers differently, eg by offering different prices or terms to similar customers if you have a 'dominant position' - not sure whether having the only AdBlue pump for x-miles would count.