Students generally start to apply for University from June/July of Year 12. Deadlines for UCAS are mid-January (Year 13), though there are tighter deadlines for Oxbridge, Medicine and a number of other courses (October Year 13). It is worth checking when looking at your courses. Many universities interview, some even use extra testing. Information on all of this can be found below.
UCAS – University Application System
London Interdisciplinary School
Unifrog – all students have username and password