we use m&s white cotton shirts for ds1. was well, iron well and last him all year. why do you say "tried m&s"? dd wears Debenhams ones, it was the only place I could get a size and style that suited her in 100% cotton (eczema) and they are great too
Agree M&S stuff comes up small (used to be huge, what happened?) DD1 has just got short-sleeved school blouses (100% cotton here too due to eczema) and she's in a size 13-14 (is 12) which fits perfectly (though is a bit wide around the chest but she needs the length)
I don't iron anything. I throw the blouses in a tumble dryer until still slightly damp, shake them out and then hang them on a hanger in the airing cupboard to finish. They end up about as crumpled as they end up by the time DD has walked to school. If anyone in this household ever decides they want ironed clothes, I will point them in the direction of the iron and tell them to have at it.