If you smell it burning your using up the clutch material or putting a polish on it so that could be why its slipping.
Some old boys drive with their foot on the clutch so you could have inherited the problem from him.
Can't you ask the council for a drop kerb, save bumping up and over?
We run new Transits, these are fitted with a dual mass flywheel and if you get them smelling ie backing up a hill, the clutch goes on them.
