If its the chick crumbs that I buy to use as cat litter, and it certainly looks similar to those, then its expensive to buy online like that £13.00 for a 20 kg bag? You can just go to an animal feed shop, or larger pet warehouse type places and buy the same amount - 20 kg for around £7 or £8 - I can actually get mine through my local petshop for £5.89 for 20kg. Its called chick crumbs, or sometimes starter crumbs. The chick crumbs as just like WBCL.
Edited - actually I've just had another look at the pic, it looks bigger than the chick crumbs I buy, more like pellets - it may well still be chick feed, but probably what they call Layers pellets, as opposed to the crumbs.