A late answer, but my excuse is that I've only just registered on the site.
If the problem is that the engine revs don't drop, or even rise, when you lift off to change gear the problem could be with the clutch switch. This widget is part of the clutch hydraulics and lives on the r/h inner wing next to the hydraulic fluid reservoir. When you press the clutch the signal from this device reduces fuelling, and also I think disengages cruise control.
Replacing it worked for me!
Jon