I did it tonight as I think it is ending soon. Anyone else done it? It's to be found on www.bootschangeonething.com
I hope I've done that correctly. I'd hate to be responsible for people hunting for it! I went to the Boots site on the MN home page, clicked home and went to the bottom left (ish). I don't know much about it (as you can probably tell! ) but I hope it is of help or interest to someone else who didn't know of it otherwise.