Thank you Snagger for that comprehensive description. I haven't actually checked the rear splines for wear, only the front when I replaced the swivel housings. All was in order on the front but then again I don't have metal flecks in the front.
The alarming thing is that quantity of flecks collected in 6 months was of a similar quantity to that I noticed when I changed the oil in April. That had been in a couple of years.
I will also be buying some magnetic plugs for the engine, diffs and gearbox/transfer box from Nige.
I will carry out the work you describe and inspect the rear diff components carefully. I think trailer fitter has some videos on youtube.
Thank you again for the help, well worth the monthly donation to the forum 👍