That is an amazing drawing and will result in a fabulous quilt!
I don't know whereabouts you are in England, but round here my first thought for getting the right fabric would be Abakhan Fabrics (they sell a mixture of different types of fabric, it is a bit of a lucky dip) or maybe somewhere like Simon Boyd (more upholstery style fabric, but some other types - plus they have off-cuts).
Alternatively, eBay, although that also has the lucky dip element in that you don't actually get to see/feel the fabric before you buy it. Or get some old white/cream damask napkins off eBay and dye them yourself?