Halls normally move in the Wednesday and Thursday before term starts, possibly Tuesday now as well since there's more halls than there used to be. The first day of term is the 3rd this year so that's the 24/25/26th, they stagger the halls so that there's not too much chaos and your first social will normally be Welcome Party 1 or 2 (whichever is on the first day you move in) and that's at the Students Union to give you chance to get your bearings on campus before being taken into town on the following nights.
Each hall has it's own Freshers week social timetable which you may get through the post but it'll also be on their website. As far as the students union is concerned it'll probably be;
Wednesday - Welcome Party 1
Thursday - Welcome Party 2
Friday - Freshers FND
Saturday - maybe an act or something but I think most halls go to Notts that night
Sunday - Sing Off and after party
Monday - Calmer night like XXX rated hypnotist
Tuesday - Freshers Stupid Tuesday
Wednesday - Freshers Hey Ewe
Thursday - Universal Thursday
Friday - Returners FND
Saturday - Freshers Ball