When I was younger I really did not need braces, my teeth were always really straight. I am 20 and my teeth are still quite straight more so than most people but still. I would like to get some braces just to correct them straight fully.

How much do they cost and would the current condition of my teeth since they are not that bad result in a lower priced treatment?
How long is the duration wearing them and is this affected by their condition

Keep in mind I live in the UK