When I did my undergrad (not medicine) I moved out for the first year, unfortunately I got stuck with a large group of girls studying drama and it was a horrible experience.
In second and third years I commuted with some friends, we were in uni 4 days a week and drove a day each per week with a 1hr 20min round trip. Despite the large commute we all stayed really involved with the nightlife and being social with our uni mates, although our university was quite small and the course was very laid back. Other students were more than happy to host you staying over for nights out and would arrange other things like barbecues, birthday parties, the usual social get togethers.
Perhaps move out for the first year, see how you feel and whether the 'experience' is worth the extra money, your parents also might enjoy having some extra freedom from your absence or they may miss you dearly! First year is more ideal as it is typically the most laid back (5 year undergrad at least, don't think the same is true for GEM) and you can enjoy freshers and meeting new people with more freedom as you state. If you don't think its worth paying all that extra money then move back for the latter years, by then you should already have some great friendships and experienced much of the nightlife, etc.