Found these in Home Bargains which I think is a national company about 80p....the down side I think there is only 5 or so in the bag( sorry just checked 8....)not bad quality and a volume gauge on the side. I bought them thinking could use them as boil in the bag but not sure now. DaveEmailed a mate of mine who had the Sainsbury's bag, and he has just replied saying that they were the bags below that he had from Sainsbury;s. He's of the opinion that they are much better than Zip-Lock bags.
http://www.polylina.co.uk/pour&store.html
Best regards,
Paul.