I am reticent to buy any actually as because of his skin and allergies he has always worn 100% cotton. I don't think that 35 hours a week in polyester is going to help his eczema any.
His school uniform is poly cotton mix polo shirt and polar fleece top, poly cotton cargo shorts or long pants, or track pants (which are cotton lined, but nylon outer). It can only be bought from one shop, and there is no 100% cotton alternative.
My mum bought him some black 100% cotton school pants (for something else)from asda for around 3 pounds and it breaks my heart to pay 3 times the price for poly cotton ones.
So do I buy him one of everything and not buy any more until I'm sure it will be okay? One shirt, one polar fleece and a pair of pants will be around $70 (20 quid).