We weren’t charging for small things like sump washer but now I have our new computerised stock control system in place we do but the cost of the service has not gone up. For us with 8 full time technicians we need to know we have all the parts we need in stock so for us it is imperative to itemise our bills. I have said this already, it is not about being charge 2 quid for a sump plug washer it is about communication and to be frank if the OP was not happy that the bill is higher than quoted the time to question it is when being presented with bill and in my opinion when you pay it you are accepting it.
Ned