the unaccountable lack of turning right which Edward II has been demonstrating turns out to be that the steering damper fitted is too short - it was restricting the movement of the steering link from the relay to the left-hand steering arm. Removing it and winding the lock stops in has resulted in an SIII that actually turns, albeit not all that tight.
Seems to drive OK without it, and in fact the steering feels lighter and easier. No obvious tendency to shimmy or anything, so I reckon I can live without a damper.
The 110 did some impressive shimmies when it's damper was shagged, but then that's a different system. Noted various iffy rubber gaiters on steering joints. Wonder if any are the same as Disco ones, I've got some of them spare... 2 RH ones, it seems, RTC 5869 I think... bugger. Paddock say 5867 for the series, 5869 for the disco. bet it's a different thread or something.