The thing is Nicked (and others), that where uniform is never worn, kids care less about what to wear each day. Yes, there are the few who are complete fashionistas, but those kids are the same about uniform anyway. I teach in a private school and you would think that it would be a fashion parade with labels everywhere, but it isn't at all. There's one or two each year who start to develop style etc, but I have never heard any kid being laughed at for cheap clothing (and we have some on assisted places who don't have much money at all, in a private school with wealthy kids) or wearing the same thing every day or anything like that. Beyond a bit of friendly banter (and it is good natured) about wearing different sports team kits, there are no problems between kids. Uniform just seemed to provide a load of opportunities - it divided those kids whose parents would let them break the rules from those whose parents insisted on sticking to them. Some families can't afford black shoes AND gym shoes, so their kids are constantly in trouble and doing detentions, or having to wear the hideous lumps of black plastic that the market sold super cheap.
I know that where non-uniform days are a big exciting thing, then the pressure is on, (and it costs money!), but never having uniform just keeps it much lower-stakes all round.