Just yesterday I noticed that my second gear has become much louder than the other indirect ones. When you engage second you can hear a slight rattle as you lift off the clutch, and as you speed up you get a whine rising in pitch - sounds a bit like a cello string being played up the scale. Third is quiet as normal.

What would this be? And do I need to get this looked at now or can it wait a couple of months until the car's annual check-up?

Thank you as ever for the suggestions.

Tom