I recommend Fabworks in Dewsbury, it's nice and handy for the rail station, and also 'Lucky Fashions' in Dewsbury, which is a small shop tucked away and run by a most delightful lady. A veritable treasure trove, it's only open Wednesday & Saturday, we can tell you how to find it if you want to go there.
there are a couple of fabric stalls on Dewsbury market, and also Leeds market. Apart from that, there isn't much round here, but there is a place over Burnley way, called Immanuels, which sells very cheap fabric bought as job lots and sold on quickly. again,, let us know if you want directions and/or company! it's housed in an old chapel (hence the name) and referred to by us as 'church'