Repeated clutch/gear problem mk7 transit

[Lawson1983M]

Hi, really need a bit of guidance on this please....
Van was great then when accelerating the revs would rise and the speed would not increase proportionately, like it used to.
New clutch needed - diagnosed.
Garage replaced clutch and slave cyclinder.
Noticed a slight clipping getting into third gear after this. Raised issue.
Several days later the clutch pedal fell to the floor, leaving me unable to get the van into gear on the Severn bridge.
Slave cylinder was replaced.
Pedal still not right, so was bled.
Problems came again- same as before. Clutch dropped and wouldn’t return.

This time they changed the master cylinder. Said it was ok, went to pick it up and couldn’t get it into gear. It was fine with the engine off, but start it and it wouldn’t go into gear again.
I left it with them again as they said they would have to look in the morning.
When they came to look In the morning they said the clutch pedal had dropped over night.

They then changed the slave cylinder again.

And tonight, I’ve had it happen again. Long drive, went to change gear at end of motorway run, and I couldn’t get out of gear or change back again.

Please help as I’m at a loss, nothing works and i don’t know what to say to the garage tomorrow. What can it be?
Thanks, Mike