Fuel surcharge question

Just had a question about fuel surcharges. Does anyone use a mileage fuel surcharge in the UK or in Europe, or is it strictly percentage fuel surcharge? In North America, mileage fuel surcharges are based on the current U.S. Dept. of Energy diesel retail price levels versus a base price of diesel. I do know that some larger companies use the North Brent price of oil as their basis for setting fuel. What is the norm for smaller companies? Thanks!

Never had a fuel surcharge, just put my prices up when diesel goes up.

I work mine out at 8mpg (for most jobs) and use the local shell garage as a price benchmark.

As this goes up, so do my prices. Must admit though, this years seen a lot of stand down days.