So the 915 gave up on me, not surprised as it took a lot of stick (pardon the pun). During spirited driving 2nd gear decided it didn't want to go in at all. I managed to limp it back to the unit and we drained the box to find a lot of dog teeth loose, I was surprised as there was no grinding prior to failure.
A few dog teeth came out with the plug, the rest from the inspection plate removal.
:D
The first and second gear dog rings had no teeth left and the synchro had fell out! Luckily this was the only damage and it was a relatively cheap fix (for a 915 box).
Now the box and engine is back in, she shifts into first a lot easier and the judder when pulling away in first has gone! Engine speed increases quicker now with the aluminium clutch housing so I'll need to adjust my heel & toe. I just want to get out and drive it before the weather gets rubbish!