Hiya, What course are you thinking of studying?
I'm at Uni and I'm 25, and to be honest I feel I don't fit in, when you're surrounded by a majority of 18 and 19 year olds. But with anything, you get people of all sorts of ages doing Uni, there's a guy on my course who's in his 50's, and in the first year a lady in her early 40's whom I was good friends with (she ended up leaving and doing a course with Open University), and a couple of 30 year olds.
Don't worry about what other students think, I think they are more interested in themselves, just concentrate on your own studying, that's what I do, just do my own thing.
I think you should go to Uni, I am in my final year now, and it's the best thing I've done, and I've learnt so much.
Good luck, I'm sure you'll do well!