[Chris152]

Is this the part that we're looking to check?

Eta - If so, I've just had a look at them, the one that the Mot called attention to is the one with the more collapsed rubber.

If I get the front of the car on stands and try to turn the wheels left and right without the engine running, might that tell me anything helpful about the effort needed to turn right?

That said, if the offside joint is indeed causing resistance when turning right, wouldn't it do the same when turning left - which isn't happening?

UPDATE! Just took it for a quick drive around and about, doing 3-point turns wherever I could and it definitely feels better - not immediately (on our driveway) but once I'd gone 400 yards I did some turns and it was definitely lighter turning right. Maybe it's the universal joints as you suggested, Bugjam. I'll keep giving it a spray a day, maybe it'll loosen still more.