The jump really depends on subject; for example, Maths and English Literature is a huge jump, whereas History in my opinion was barely a jump at all. However, expect the jump to be quite high. It is possible to do well whilst having a social life, though harder than it was at GCSE. My tip would be to do as much homework and revision as you can at your Sixth Form so you don't have to as much as home, so you can have time to relax and hang out with friends.