Gearbox or Clutch issue?

[darrell]

1987 5speed 1.6 Diesel
recently got stuck in 4th accelerating up a sliproad, managed to pull it out a day or two later, got in and out of other gears ok but kept getting stuck in 4th (about 3 times). Drove to work and back so my bro who's ex mechanic could look at it (4 miles at most?)
A day or two later whilst looking at the problem I couldn't select reverse either. I hadn't been driving it but manage to limp to local garage (another 4 miles?)
They replaced gearbox oil and welded a part on the linkage they said was broken. All for £50 but said the gearbox is knackered.

After this visit driving it was very different, gearstick very stiff but managed to get back to work (another 4 miles)
In reverse the van judders whilst clutch is depressed at all but runs smoothly backwards with clucth right up. Forward seemed ok if hard to select.
My bro looked at it and found the clutch slave cylinder was leaking and today we finally replaced it and bled it but the problems still exist.

We have noticed there seems to be no neutral. If I pull the gearstick out of a gear and lift the clutch, the van tries to move, wiggle it around some more and same problem.
Whatever gear I'm I can stop the van moving with the clutch down, but at this point with the engine running but van stationary, my bro tried to push the van and it wouldn't move, just as if it were still in gear. This applied to reverse and 2nd (treated like 1st on 5spd) gears.

I spoke to Aiden on the phone who certainly knows his stuff but I'm not sure I can afford a rebuild or if that is exactly what I do need.

Problems seem to point to clutch and/or gears.

I've seen 2nd hand 4speed gearboxes more often for sale than 5speed but I'm worried this could affect other things that I'm not sure of.

Anything I can try before passing this on to the pro's?

Thanks y'all.
Darrell