Can anyone tell what chord sequence Jon Boden's playing here?

In the month of January (A Folk Song A Day)

I think the tune must be a bit different from the ones referred to above. I've been trying to follow along on concertina and it's driving me mad. The changes sound straightforward, but every chord I try to plug in (after the first one) just sounds wrong. (I'm playing an English concertina, so there shouldn't be any notes I can't get.)