My view as one who went to schools with uniform and as a mum who has a six year old son about to transfer from school with uniform in the UK to no-uniform in Canada.
As a child, I remember being proud of my prep school uniform, I remember that our senior school uniform was so relaxed that we 'expressed' ourselves in the most hideous ways (anyone remember white fishnets over black tights?). Almost all schools in the UK have uniform, so our attitudes are probably different from in other countries. Our uniform is part of our 'tribe'. In the streets of south London you kept in groups of your own uniform - good or bad? I don't know?
As a parent I LOVE uniform - it's easy to organise for the week, it's cheaper than buying regular clothes, and it avoids all competitiveness about what is cool and what is not.
And as a regular volunteer on school trips, uniform is invaluable. Keeping track of a swarm of little people is easy if they're in uniform..... But well nigh impossible when they're not.
Does it bring about better discipline in schools? Of course not - that is down to the quality of the teaching staff, and the level of support they get from the parents.