Not that I really took part in Freshers at all, I'd hate it.
University is your opportunity to meet new people, and start the rest of your life, and Freshers is a huge part of that! If you attend events with a group of friends, you'll not meet as many people, and you might miss out on those initial steps that forge friendships that will last forever!
Your friends made the decision to stay at home (or failed to get into Uni, in which case I understand a bit more their enthusiasm) and they shouldn't expect to elbow their way into your future. If you're really close, you'll stay friends despite making new ones at Uni, and if you're not so close, don't even consider letting them come! They should understand that even though you want to remain friends with them, and do things together, this is the first opportunity for you to make friends who will be there for you when these friends cannot - for things related to study, your University and the local area. If they don't get that, time to move on anyway!