ok so, long and the short of it, looks like there was some serious ingression of sandy water from the flywheel back...
so:
Clutch / Flywheel - can't tell until the transmission is off, but given the fact that the wading plug was packed full of fine sand when i removed it, and given the slapping chattering noise it was making and the clutch pull away judder it developed i would say at the very least clutch release bearing and clutch plate gone
transmission: - oil came out fairly clean, some swarf on the magnetic plug (last changed around 10,000 miles ago), could be ok but simply can't tell without taking the box off and checking
transfer box: f*cked. pulled the magnetic plug out and it looked like a chistmas tree, not just with fine particles but slivers and chunks of steel attached so looks like that has failed.
i did get home under my own steam, drained the oil out and checked plugs etc. I was going to flush it through with some ATF and then change the oils but given the state of the plugs and the noise the clutch was making i just didnt think there was much point in spending £50+ on some oils for flushing, and then a fresh change when it might need some far more serious TLC
Long story short, it may well be a trip to ashcrofts for a new clutch, gear box and transfer box. Joy....
failing that i'll (somehow) drop the box off myself and see what the damage is, maybe try pick up a new box of flea bay.
aside from that, good day!!