Jim
Interesting you have done a S2 gearbox oil change. Can you confirm the filler is indeed on the passenger side and did the filler and inspection hatch line up! I think getting the oil in with tube and funnel might be ok but trying to undo the filler plug might be a sod.
Yes the filler is on the passenger side just above the drain plug. You can reach it with a plastic pipe to fill it from underneath if you can raise you car up of the floor. I used a plastic hand pump from machine mart £20 it has a loop with it that can be hung in the filler whole. Fill it until it overflows, it was around 2 litres I think. I used millers gl-5 ep 75w 80 mineral, this was recommended buy Phil at Brands Hatch Morgan.
Regards Jim.