I have tried the published procedure - hold messages button til spanner flashes then touch again. I have now a few hundred miles or 13 months to next service, which is obviously drivel. Service done just want to reset it (myself). MY16
As my main dealer can't service the car with a roof box fitted, I have just settled for an MoT (elsewhere) and, having only done 3,000 miles in the last year (mostly EV), see little point in worrying about the service (basically an oil change) with only a year left on the warranty.
As the service required message disappears once I start driving, I can happily ignore it.