Nick
I found these links which might help explain the levels,
http://en.wikipedia.o..._National_Certificate
http://en.wikipedia.o..._National_Certificate
In my day, a long time ago, when there were also Technical Colleges, rather than all Further Education establshments being Universities, the ONC/HNC/OND/HND route through the educational system was considered by Employers to produce more practically biased employees, and the degree route to produce more theoretically biased employees. In my humble opinion, by making all Further Education establishments Universities has lead to a dumbing down of the value of a degree, and thereby disappointing lots of new graduates, whose job expectations had been falsely heightened. It has also lead to a situation where "self-funding" is now an issue, rather than State funding for the most able.
Rant over, hope this helps. I would suspect that by going the A-level/ONC/HNC route you will place yourself in the job market as being practical. I believe that many HNC courses also include work experience time, very valuable. My own first degree did that. You might even find that the Employer with whom you do work experience will take you on after you finish your course.
Sorry if I have waffled on, but I wanted to be as comprehensive as possible. I apologise for any typos! Good luck in your career.