I am currently working on a MK2 Punto that I bought on the understanding that the clutch had gone. Turns out the clutch had been changed recently so I think the previous owner had then run out of ideas.
The car goes into all gears fine but there is no drive except it did try a little in revers. On axle stands again revers gear seems to work a bit better as there is now no load on things. First gear even had a try (about two revolutions of the driveshaft) before stopping. No odd noises or anything.
Anyway I have taken the box out and the clutch looks pretty new. I have now dug a bit deeper and split the gearbox casing. I was hoping to see something obvious. Maybe some big chunks out of the teeth or a bearing hanging off etc but nothing obvious jumps out at me.
Has anyone come across anything like this before. I do very vaguely recall something about slipping diff crown wheels ?? Any help or a point in the right direction would be appreciated.

There have been a few posts about the crown wheel slipping on the diff cage. Can't remember the detail now, but if they are an interference fit, they might let go.
Also check the diff cross pin is not broken.

See what a search for diff will bring.

Here's one: https://www.fiatforum.com/punto-ii/240714-diff-crown-wheel-slipping.html
There are more.

Thanks for that. I have had a closer look at the diff and its definitely cream crackered ! The gear (crown wheel I think) spins freely when obviously it should not be doing that.
This would explain it !