Lurker is right, most parents do want uniform and enforcement. And I'm sure there's no will towards relaxing uniform from parents or from government.
Based on our experience, I think that the drive behind more and stricter uniform is based on totally fallacious reasoning, rooted in some kind of weird folk-memory that harks back to a fictional time in the past when all children were neatly dressed in blazers and caps, knew all their times tables and their place and gave up their seats to adults on the bus.
I think this because any time (every time, you can set your watch by it) the fact that you have a child at a non-uniform school comes up in conversation with other parents, you can guarantee that the conversation will go: "Oh, I love uniform, I'd never send my child to a non-uniform school because they'd get bullied for not having the latest designer wear/they'd spend hours deciding what to wear every morning and never get out of the house on time/children need something to rebel against, if it wasn't uniform they'd all be smoking and taking drugs". When you point out, mildly, that this is in fact not the daily experience of having a child in a non-uniform school, their eyes glaze over.
So there's a weird kind of self-fulfilling circular logic that goes, 'uniform is a good thing because we believe it's a good thing, therefore it must be good'. Of course it's bollocks, as witness the many many education systems (and a handful of brave establishments holding out against the tide in the UK) that don't have uniform and still manage to have orderly, rigorous schools producing well-qualified sensible school-leavers. And of course children who have grown up in a system based on uniform will be more than averagely likely to push the envelope when the rules are relaxed or abandoned for the day (witness the other common argument, "Oh, non-uniform day is a nightmare, I couldn't bear to go through that fuss every day", which completely ignores the fact that having a single random non-uniform day is in no way the same as not having a uniform at all).
I don't normally even bother trying to have the argument with people tbh, because it's pointless. Most people who argue for uniform have never experienced life without, so they have nothing to compare it with. Short of decreeing a compulsory RCT of splitting all UK schools into evenly-matched groups, making half of them abandon uniform, and then doing a 10year follow-up, nothing is going to change. Besides, I think parents secretly like having something to complain about. 
But honestly, if you have the option of a no-uniform school, grab it with both hands, it's a revelation. 