Possibly, but it's the parents' job, not the school's, to see that children dress properly (however that is interpreted). UK parents expect the school to do everything and (wrongly) believe that it is more influential than the home.Kids wear what is fashionable - baggy jeans and t-shirts for boys, for example. If their parents forced them to wear proper trousers or even polo shirts, they'd despise it just as much as a uniform - except they'd despise their parents too.
I'm sure this is true (and has been so for a long time).People on the continent dress better because you're allowed to care about how you look without being labelled gay or metrosexual. In the UK, as a teen, if you care about your appearance, you get teased. That's how it was when I was at school in Wiltshire a decade ago, that's how it is now (or so my younger friends tell me).
The rest of your posting raises the important sociological issue of the need for parents to reclaim authority over the peer-group. I agree with your analysis but am sure that school uniform is not the answer; the equality argument for uniforms is a spurious one - children sniff out the subtlest of differences - second-hand uniforms would be mocked just as second-hand normal clothes were.