You need to set your stall out accordingly. Vans have to purchased, taxed, insured, serviced, mot'd and depreciation accounted for. I think if I ONLY worked locally only say up to 20 mile radius then my hourly / daily rate would have a proportion built in. However we work all over the UK and even Europe therefore we charge 0.45p + VAT per mile on all travel. We also charge for Parking and any tolls or congestion charges. This said I think it has to be applied appropriately for example if my Window Cleaner said it is £25 to clean your windows and another £5 for mileage I would probably tell them to do one as that is 20% and I see it as disproportionate but if they said sorry Kev prices have increased slightly and your charge has gone upto reflect this to £27 then I would probably pay it. Likewise if I moved and wanted to keep my Window Cleaner because I liked them and had moved say 15 miles and they agreed to continue cleaning my windows for an additional £5 to cover fuel then I would pay it in that situation as well.!!!!
It is all about the way you put it over to the customer in my opinion
Kev