In 2012 and 2013, I knitted dozens of these, even saw one of them in Sainsbury's on it's Innocent Smoothie bottle. Mine were fairly basic, but included a few made-up animal ones. I hadn't seen those patterns in the link. They are very quick and easy to do and helped to pass the dark evenings. I see the deadline is in December this year, previously they had to be in during October.
I was a bit disappointed that they sent me a thank you card. I would rather the postal cost went to the charity.
This year I have been knitting squares to make cat blankets for Battersea, which also use up my many oddments of wool.