GCSE - school subjects you do at age 16 in england, wales and n ireland (not scotland). between 9 and 11 subjects, usually.
A Level or A2 - two year course from 17-18 (final years at school). first year of known as AS level. usually do 3/4 subjects. grades needed for medicine are at least AABb ('little' b is an AS level; most peopl only carry on three full A -levels) but most have AAA
not sure about UKCAT scoring. only introduced a year or so ago.
