Having put the car partially back together I discovered that although the wipers then correctly parked when switched off (the original fault) the intermittent wipe feature was no longer, intermittent. It caused the wipers to be on low speed constantly.
Having resigned myself to the need for a new switch, time being the awkward bit about it, not the £9 expense, I realised late last night that I had one more switch not in use and easily accessible. Now, having raided the switch from the silver car, I have working wipers and a new switch on order for the silver car.