I always buy high thread count poly cotton sheets , Percale & Egyptian cotton are great . I also like the high thread count ‘ sateen ‘ fitted sheets from Asda . I don’t think it matters where you buy them from as long as they have the above quality .
We have Christy sateen fitted sheets which are excellent but they also do a 48/52 polycotton range which I'd imagine are good quality. www.christy.co.uk/bedroom/bed-sheets
When it somes to bedsheets Percale 500 thread count 100% Cotton bedsheets are the way to go. so nice to sleep on and they wash well, I made my own, purchased the fabric online.
Poly/Cotton bedsheets are normally 65% Polyester 35% cotton, 68 pique thread count, budget bedsheets, Big ASDA Stores ot Tescos have plenty of them in colours.
If the poly/cotton belnd is not right the sheets start pilling.