just to report back, ordered 2 x sets of Orings from Blue City Motorcycles..had to order them for a 1993 bike as there were no STs listed for 1994. Order arrived swiftly and got around to removing rear wheel a couple of weekends ago and cleaning/regreasing splines with moly paste and replacing Orings...old ones looked to be fine, but I swapped them out anyway.
the bloke on Youtube took about 15 minutes for all this, I spent a good 3hrs as I undid the wrong brake caliper retaining bolt in the first 3 minutes...reviewed instructions and fixed my mistake and carried on..! Still, next time it will be 2 hrs, then 1 hr...
Slowly building confidence to tackle basic maintenance on the bike...