Very faint whine, increases with revs in 5th gear when coasting down a hill. Stops when clutch depressed.

Can't hear when on power or in any other gears. Could it be anything except the gearbox? Had this box replaced not long ago :'(

Any one got any ideas? Cheers

1.9 mjet sporting, less than 3000 miles on new box.

Has to be the box. Audible whining/rattle when stationary, disappearing on disengagement of clutch? Perhaps not yet as that would be the final stage.
Probably new here is not factory-new, that would be really schocking, but it's still very disappointing with just 3000 miles.

Yeah, all signs point to box, was just praying it could be something else haha.

Box was a recon unit, all bearings replaced with upgraded ones and any worn Synchros replaced. It's still under warranty so ill give them a call.