I started uni in a relationship and I don't feel it has affected my uni life in a negative way at all.
Me and boyfriend had already been together for about 2 years before starting uni, so we were well past the stages of needing to be with/speak to each other ALL THE TIME.
While at college, we also made the decision of not letting our relationship affect our decisions about university. If one of us wanted to go down the opposite end of the country, then fine. If our relationship survived, then great, if it didn't, then at least we hadn't ruined our future.
As it was, we ended up going to uni's in neighboring cities.
I think personally the key to balancing uni and a relationship is maturity. You have to accept that sometimes that you aren't going to see each other/be in contact all the time.
Yes, it kind of sucks when I have to text my boyfriend and tell him I can't come and see him this weekend because I have a huge essay to write, but when I get good grades, I know it was worth it.
And yes, sometimes he won't text me back for hours and hours; he's probably busy with friends from uni, just like I am a lot of the time.
I've just passed my first year of uni with a 2:1 (kind of annoying it doesn't count for anything!) and I still have a very happy and healthy relationship with my boyfriend.