White cotton, made in India, best cottons I have ever had have been Indian.
I don't care where they are from in the UK, usually a department store, Selfridges, Harrods and once, Heals. I mean the high thread count, not the pretty painted patterns. They are smooth, wash well and last ages. The ones I have don't rustle. They have applique or embroidery so not completely plain. Plain white sheets, vintage cotton, or metis linen from France.