@Iminei I have to admit I'm not really sure what those words mean
Although from lurking in the darkside I can sort of get what they're describing, I'm not sure what their different uses are. I know the colours that I want to use, I'm just worried about different shades / tones / patterns looking odd together because I don't have much of an eye for colour and wouldn't do anything remotely contrasting normally.
I think the bigger fabric shop in my home town will cut in 25cm lengths, and has quite a big range of cottons, would that still be useable rather than fat quarters? I'm sure there must be somewhere in London that I've missed but most of the fabric shops here seem to be dress fabric. If all else fails my stash growing a bit isn't the worst thing to happen