Just been reading through US Safety Recall Bulletin SR-18-002REV (Google it - a pdf that can be downloaded). So if the mechanism is not too rusted does that mean that if the entire caliper is not replaced that the replacement handbrake mechanism lever is a modified item (or possibly, as far as I can make out an additional O-ring might be used) and that therefore the problem won't re-occur? As far as the 2mm 'correct operation check' of the lever is concerned mine appear to be working perfectly well at the moment as A) my PHEV has only done 16,000 miles and B) I've frequently cleaned the calipers, squirted silicone spray on the moving parts of the handbrake and smeared silicone grease around the rubber handbake mechanism seals.
So I'm betting I won't be getting new calipers, more likely just the adjusters. Although as the recall notice says it'll take around 2 -hours I'd be surprised if each mechanism could be removed, cleaned-up and replaced within 2 hours.
I don't know if the UK procedure is likely to be the same as the US though, You'd have thought it would be. According to the bulletin SR-18-002REV (dated April 2018) it supersedes bulletin SR-18-002.