This is your choice as a business, not dropping prices every time wholesale prices do is theirs. The business model is quite a simple one...at 4p a litre profit they make about £1.80 per average 45 litre tank which is buttons really. However they can sell possibly hundreds of tanks of fuel per hour and that is how they make cash. Currently they aren't doing the volume part of that equation so they need to do something cos the bills haven't stopped as you've noticed.
I assume you set your prices at a level where they cover your overheads + some profit to cover your time and effort and don't just sell at wholesale otherwise it's not a business it's a charity. Against a background of sales dropping off a cliff you expect another business suffering the same to reduce their revenue to help you out?
Petrol stations are very competitive business there was 40,000 50 years ago, there's about 8000 now and they were going out of business at a decent rate even before this.
https://www.itv.com/news/2020-04-01/petrol-stations-will-have-to-close-due-to-impact-of-covid-19/
I would imagine you are in a difficult position at the moment but you also have to remember lots of businesses are.