Depends, are you talking about commute? I'd hate to live more than 30 mins away if I was commuting everyday (although I'm lucky that my college doesn't have any accommodation more than 25 mins from the college.)
If I'm living at uni, I would travel any distance within the UK if I was on a lease that allowed me to stay in the vacations. Having to move in and out each term (as I currently do)? Probably not more than 5hrs either way. I currently live about 3 hours away by car, which is nice because it means moving in and out isn't too much of a hassle, but my parents can't surprise me with a visit.