During a semester of studying abroad in London during my undergraduate degree (#1), I went out dancing at the clubs quite a bit with my friends. We enjoyed ourselves...but I dropped a ton of money on drinks; I think that made up most of my non-tuition budget! We always had to dress up when we went out because the clubs required smart attire: no tennis shoes (trainers), no jeans, and nice-looking clothes were required.
I have no idea if this is still the case in London since when I went out dancing there was in the last decade. However, I can say this: I enjoyed my time out dancing in Germany better. We went out for Halloween and I asked my friend if there was a dress code. I just wasn't feeling like dressing up (it had been a long week) and I wanted to wear jeans and some Chuck Taylor-style shoes. I was in luck: I could get into any of the clubs in the area wearing that.
We went out as a group, dressed as a wide variety of weird things for Halloween and went dancing at the club. It was much more relaxed-feeling, too. I was not interested in meeting anyone at the club; I was there with my friends and to have fun. Some people tried to dance with me, but I politely excused myself. I'm just too old* for all the silliness that goes along with clubbing/trying to meet people so I enjoyed it purely as time to spend with my friends.
*Okay, I'm not middle aged or anything, but I'm sooo over being a college student in my early 20s.