I’ve just had my scoot serviced at an independent garage and now the “oil change” warning is showing on the display. How do I get rid of it, please?

try this-

Ignition switch ---Off
Push the "ADJ" Button (under the Rev Counter) , and turn ON the Ignition, wait a couple of seconds until the indicator blinks and goes off, turn off ignition, or, go for a ride!
(Sometimes the handbook gets it a bit wrong and confuses the two buttons, there's one (SEL) under the Speedo too.-but I think that one resets the Trips)
ps. You have to push Both buttons to get into the Clock Reset mode!.

Lets know how you get on.

Cheers, Robin.

Worked a treat - thanks, Robin.

That's good to know, thanks for confirming it worked.
Robin.