Its funny they never miss giving you the bill thougha lot of things can get missed during servicing but changing the oil and filter is a must.
Peter Vardy Jaguar in Aberdeen did the annual service on an XJ a few years ago.I know of a lady whose hatchback was taken to its supplying garage/dealer in north Down for a service.
A while after that it broke down on the motorway/dual carriageway, recovery man said the sump plug was missing/there was no oil in the engine.
a lot of things can get missed during servicing but changing the oil and filter is a must.