VAT Number
IO540 - No one mentioned the word 'commercial'. We just asked for Avgas.
The refuellers insisted on a personal tax number, we tried a National Insurance number - no joy. We tried the number on an EHIC - no dice. Eventually someone phoned home and got a valid VAT number. Armed withg that they were very happy to fill all seven aircraft and this number worked on every airfield. So long as you have a working VAT number that is accepted by their computer - no problem.
It was never a question of no number = fuel+VAT, it was no number = no fuel.
Why?? Don't ask. Don't know.