I love knitting; it keeps me sane some days! Crocheting, too. In fact, my when my stepbrother was young, he never knew which I was doing at any given time, so he would just ask if I was 'yarning'. I still use that term.
Anyway, for really great prices on yarn here, I go to Fairfield Yarns. They buy and re-sell surplus yarns that manufacturers aren't using any longer. It's family-run, and the fella who is always in when I go is very friendly and knowledgeable. It's in the Greater Manchester area (near Rochdale), but they will dispatch all over the UK, if you have some idea of what you want. I love it there; they have massive amounts of yarn, and since they buy whatever manufacturers are done with, every visit tends to be a surprise with something new. One time I walked away with 2 kg of Shetland wool for just under £25! They always have some really, really gorgeous wool, too.
Definitely give them a look sometime.
http://www.fairfieldyarns.co.uk/