Diesel is imported rather than it all being refined in the UK. Diesel has additives. The US ‘driving season’ has ended meaning they have stocks of petrol they can export. There are more diesel cars on the roads in Europe creating the usual ‘greater demand = higher prices’ business model.
I have a (golf) friend who owns a coach company - circa 50 coaches - spare a thought for him; he tells me he is now paying 100,000 euros a week for diesel !!
Scroll down to 'What makes up the cost of a litre of unleaded petrol?' and 'What makes up the cost of a litre of diesel?' for a full breakdown of where the money goes, based upon current average prices:
https://www.rac.co.uk/drive/advice/fuel-watch/
ZM: "Then there’s the Ad Blue costs as well, Khandro, which has tripled in price recently in UK. " - Which is ironic because ADblue is largely made from urea, of which there is an inexhaustible supply!
OG; //Does he get the custom much during the winter months ?//
Apart from holiday excursions etc. he has the franchise for a lot of the public busses in the Black Forest region.