Quids in?

Lot of air time on breakfast telly yesterday about the new pound coin which is being introduced today.  The big question being posed was whether the innumerable coin-in-the-slot machines will have been converted in time.  But it seems to me that the more crucial immediate practical question is whether those that have been converted will still work with the old pound coins?  I shall be going shopping tomorrow and it is most unlikely that I shall have received any of the new coins by then, so will the supermarket trolleys still work with the old ones?  If not, I'm in trouble!