I finally succumbed and bought some of the lovely t-shirt yarn I'd been eye-balling on The Chunky Hooker. They were very lovely and made me up some of their triangle packs in the blue, green and grey colours I was looking for.
I also bought some Hoopla and Trapillo yarn to go along with them as I plan on making a rectangular rug for the side of my bed. I'm extremely excited to try this out as I haven't used t-shirt yarn before. I don't know why using materials other than wool hadn't really occurred to me before, but now it has I've got ideas for projects with fabric, plarn and garden twine.
I'm probably only a quarter of the way through all the crocheting I need to do for Christmas and I'm itching to get started with these, but I'm going to be good and actually finish a project before I start another one!