Well, today I have completed the gearbox oil change to Castrol Syntrans.
A quick 20 mile test drive confirmed that it is quite a bit smoother than the ATF that was in before.
Just over 2 (maybe 2.2) litres of red ATF came out and 2.6 litres of Syntrans went in.
As the filler is on the right, I fabricated a length of hose pipe with a funnel attached fed down from the engine compartment and deftly pushed into the filler hole.
Then, the first two litres was easy, but I recruited my better half to pour the last half litre or so while I watched underneath.

That’s the last of the oil changes now. I am grateful for all your advice and comments. Although I was a mechanic in the army, that was a long time ago and I feel very much the novice now.
I still have an intermittent stall, which I feel is related to a battery drain, but I will know more when the auto electrician has done his thing with it next week.
At the moment I am quite pleased with myself and the car.
It is a journey and I am enjoying it.
Over and out.
Phil