It must be 100% cotton and preferably have a Victorian type pattern on it (raised cotton pattern). But it has to be plain white and not contemporary (no swirly bits or circles). But not a huge pattern or it will take hours to iron.
I have found a few extortionately priced ones on the White Company website but would rather pay 50-60 pounds not 90-100.
There is one on Ebay for 55 but I can't really see the fabric in the photo.
Thanks