Thought I would update this.
Finally got round to changing the manual transmission fluid.
Went with the G052 527 A2 (newer version)
There was no problem with shifting it was purely a maintenance thing
The old fluid looked dirty in comparison but I was pleased there were no nasties, sludge or other stuff which came out. In fact apart from the colour it was pretty good for 13 year old oil.
The drain and fill plugs were taper seat type 10mm hex (so no sealing washer needed)
I got 2.15 litres back in before it started to emerge from the level bung.
Shifting remains good both cold and hot and perhaps overall the gearbox is a little quieter.