In reply to Indy:
I have no other sensible way of commuting, so no choice here. So far this winter has not been particularly icey, only a couple of slightly scary moments in the mornings, but I am ever hopeful that it will get colder, so want to be ready on time for it. Winter tyres are on the car, so inclined to think they are a good idea on the bike.
Interesting that there has been no particularly strong views on them, that is unusual for a gear question!! Maybe it is not as significant a difference as I thought it might be.