Probably is the clutch. My van has started slipping under power in fourth and fifth, now 3rd is affected, but still hard to get any slip in first or second (yet)
Suprisingly difficult to drive in snow and ice when you can’t work out if the clutch is slipping or the tyres are spinning out!
New clutch on Wednesday, I’m not doing the flywheel unless its out of tolerances as its £360 for a clutch, but nudging £1000 for clutch + flywheel. I figure its worth gambling on £200 of labour at a later date if there is a fair chance I won’t need to spend £600 (parts only) on a flywheel.
P.S If the clutch pedal is lower than normal, that could indicate something is seizing up and preventing the clutch working properly.