[Odd Job]

I've recently had my clutch replaced on my diesel, 3 piece kit, friction plate, pressure plate and concentric slave. The DMF absolutely fine.

When I picked the car up the pedal didn't feel too great, the gears hard to select without grating, easy to stall, pretty much how you describe your symptoms.
so with permission off the garage as not to invalidate the warranty I bled the clutch. All was fine that day, but the following day I had issues again in just the same way. I'm obviously not using the car at the moment as I don't want gearbox failure to be added to the issue.

It goes back in this week to have a new master cylinder fitted. We believe that air is passing the seals on the master cylinder.

Like has been said above, any garage worth a jot should be able to diagnose a hydraulic issue by having a go at bleeding the clutch first without removing the gearbox.

Sadly on the diesel clutch issues are far too common .

Best of luck with it, hope it doesn't cost you an arm and a leg!