I didn't have a uniform at school and having visited the UK lots as a child (had family here) thought they were horrendous and was eternally grateful we could wear what we wanted. As a parent of course I do appreciate uniforms as they are easier and get rid of the stressful "what can I wear today" routine. I do largely agree with the uniform concept from that point of view.
What I don't agree with, is that a uniform raises standards - coming from a country that had no uniforms and very high academic standards, I find this idea complete tripe. I went to the best school in my country and we all wore tracksuits and scabby jumpers to school, I always laugh when I look at the old pictures, we looked a complete mess!
There are also some (rare) private schools in this country that don't believe in uniforms and do rather well, I am thinking of Bootham in York as one example.
Culturally though I think the British are obsessed with uniforms, I remember noticing uniforms everywhere in this country, estate agents (!), travel agents, banking staff, everyone seems to have one! So I do believe is largely a cultural thing, but really it has nothing to do with raising academic standards.