I think there are as many opinions around as there are shops you can buy uniform from.
I personally found that M&S offers the best for me. Easy to get (order and pick up near work), one of the few places I get pure cotton for shirts, washes well and fairly good cut.
I have now 5 of all, I wash dark and white separately and never had issues with shirts getting grey. I think we are lucky as I so far got all pen marks out when DD was in Infant but not in Juniors now where they have their own pens and some at her desk do not use the washable ones.
The only time I had to throw away a shirt was when DD came home from forest school and the shirt was covered in dried mud.
I only bought logo cardigan as a treat. We get ours via M&S and I actually find them less good quality wise then the normal M&S ones. I wash them in the same way and they look less nice far faster.
I buy to fit, I may spend a bit more but I hate DD wearing items too large, it doesn't look smart.
Shoes - I buy when necessary, regardless of the time of year. I think we bought in July, yes I had to replace in October but what can I do, I doubt buying in August would have made a difference and shoes to large do not work.
I haven't found a pair of tights that do not bobble. Next year I may try JL.