uk college age

If you turn 16 during the school year (between 1 September and 1 July) you can leave school after 30 June.
You can leave school on the last Friday in June if you’ll be 16 by the end of the summer holidays.

Applicants who’ll be under 18 on admission should seek advice from a College Admissions Tutor as early as possible to discuss their application. If they’re considering Medicine, they should also read the advice regarding age requirements for this course in the Medicine course entry.
There’s no age requirement for admission to Cambridge, although the vast majority of undergraduates are 18 years or older when they start their course. If you’ll be over 21 when you start your course you are classified as a mature student.

References:

http://www.undergraduate.study.cam.ac.uk/applying/entrance-requirements/age-requirement
http://www.goodschoolsguide.co.uk/