My local Asda were giving these away for free today. They had about a stack of 500 of them at the front of the store, and there was a yellow box that said "Free" in the magazine section too.
I asked CS if this offer was available in other stores, and she said yes. So worth checking and picking one up if you are inside an Asda store.
Hope this helps someone.
Seems to be in Tesco, Morrisons and Co-op.
I should imagine Sainsburys too.