UN1 Gearbox Help

To date I have done about 100 miles on my car since the IVA Test. All going well till the other day, started it up, but it would not go into any gear,(Lots of grinding). If I switch off the engine put it in gear then start it up, bring up the clutch and I can move off, but it wont change gear. Checked the clutch arm and that appears to be moving ok. Possible that the needle rollers have been trashed and then locked up the shaft, but I took the gearbox off yesterday, and they are perfect, any ideas. The clutch will come off today to see if anything untoward is going on there.



That's an odd one, does not sound like the clutch as its seems to be working as a clutch, allows you to start with clutch down and then drive off and clutch down again. I had issue with the needle bearing on mine (it locked) but that was due to the carrier being too short so the shaft was not far enough inside.
As you mention worth checking and also worth removing the rear cover plate and checking the selector forks, etc some useful phtots here
I have had a fair bit of head scratching with my UN1 but last night I actually drove it up and down the workshop in all gears!!