Thanks for all the suggestions and help. I have written to the garage( recorded delivery) and asked for their observations. I think I have covered all the points you have made but I will post on the outcome.
Reminds me of a work colleague in Rotherham who tried to fill up at his regular filling station during the petrol crisis. No petrol signs were up but as he could see it from where he lived he saw that it was only available for Asians and their taxis.
Just a thought but I once filled my one series up to the brim which I was told it would cost around 77 quid then when I looked back at the pump it was at 93 quid? I then realised some cars are fitted with an overrun and realised I wasted 16 quid on the garage floor!! Fair to say asda fueling staff weren't too impressed!