If it were me I'd say it was the gearbox, because when the car is in gear, there is no slippage under hard acceleration.
But I've had a mechanic look at it but he thinks the clutch has had it, that the spring prongs on the clutch don't release the clutch from the flywheel properly. I'd want to get a second opinion. I'll be going to another mechanic tomorrow.
Floormats haven't not changed. The gearbox's coming up to 212,000kms as far as I can make out. I bought the car in April at 208,000kms, no idea of previous history. When I bought the car its clutch biting point was already near the bottom of the travel down on the floor. I have not noticed it changing/getting hard. Double clutching doesn't help to ease the gearshifting.
I learned heel-toe on this gearbox so the clutch probably had more engine-braking stress than it ever needed (when I mistimed the shifts). But I never crunched the gears (ie let the clutch out before slotting the gear in). Any idea how much a gearbox would cost from a wrecker?