Hi Graham,
Just my views on this one....
To be sure what the course of action would be, more information than "on the wrist" performance is required. You really need to know if there are one or more positions that are far from the others to determine how serious the problem is. If you want to take the trouble of timing this in various positions and letting us know the result, I could provide further comment. If not, I understand completely.
If you wind the watch manually say 50 times via the crown, place it dial up, note the time and check it 24 hours later, then repeat for crown down, crown left (noting the variation over 24 hours each time), that would give us a good indication. You can also do the ame dial down and crown up if you like, but the other 3 are more important for "dialy wear" IMO.
I am not a big believer in the "settling" of a movement. IMO if that does happen it's over a few hours say after a service/lubrication rather than over weeks or months.
Cheers, Al