Check out
Fabric Guild here in the UK. Their fabrics are reasonably priced. John Lewis has a lot of half price Amy Butler and
Lady Sew and Sew always has sale fabrics.
Hancocks of Paducah will ship to the UK for $10. I just got two quilt backs for £36 including shipping! The equivalent would have cost over £100 here! You do however, run the risk of Customs and Duty, but even the few times I've had pay over the last few years has been worth it.
Happy quilting