It's possible to succeed in print journalism without any formal qualifications, simply on the strength of your writing but I wouldn't recommend it as the preferred career path. (University is seen by many as the best route; other options are considered in the links below).
Information about a career in print journalism can be found here (for newspapers):
http://www.learndirect-advice.co.uk/helpwithyo urcareer/jobprofiles/profiles/profile1459/
and here (for magazines):
http://www.learndirect-advice.co.uk/helpwithyo urcareer/jobprofiles/profiles/profile124/
For broadcast journalism, see here:
http://www.learndirect-advice.co.uk/helpwithyo urcareer/jobprofiles/profiles/profile1351/
See also the careers information on the NCTJ website:
http://www.nctj.com/career.php?career_id=caree r_id
Chris