Whilst it's always good to replace suspension and brake components in pairs, sometimes there isn't always time to do it immediately, but I also gave the nearside rear a decent inspection to be able to plan ahead, but with no obvious issues found.
But thought best to give it a second closer look - and found a clear crack on one of the bush housings. Hard to see, particularly when the rear of the vehicle is jacked up via the crossmember, as the wishbones drop down, hiding the crack.

Nearside rear, looking rearwards, first inspection

Nearside rear, looking rearwards, second inspection
Brickwerks comments on this component states:
'Corrosion on the originals starts from the inside and works it’s way out so by the time you see it it’s too late.
And we know from experience that MOT tests don’t always pick up the corrosion – usually around the rubber mounts'
I now concur with their comment and encourage closer inspection!
I found replacing both suspension wishbones (and inevitably the brake backplates and some brake components) quite a challenge (including cost of parts, needing to cut off some seized bolts, other local works identified) but recently completed it with success. I planned ahead, checked YouTube vids, got my wife to bring plenty of tea and snacks down to the garage etc which all helped.
We've since got back from a short trip with the van loaded to the gunnels with people and stuff: doesn't bear thinking about 'what if' on the old degraded suspension wishbones.
Hope these observations are helpful to others.