In my second year I was a mentor to a first year 17 year old. While she couldn't go out drinking with older students, she still joined societies and made friends with her course and flat mates. It's not like you won't have any chance to be social. If you want to join in with the drinking, join in with pre-drinks. Of course, if you don't just want to drink other people's stuff, you can give them money to buy stuff for you and then join in with pre-drinks. I personally wouldn't argue that you can still try and get into clubs and stuff considering how much they ID people.*
*For all and any that get arse-y about being ID'd despite being over the legal age requirement, please stop complaining. They are just doing their job. Most places have an age limit they need to ID for, such as 25. If it is their opinion that you look younger than this, they will ask for your ID. It doesn't matter what you start shouting about, or how old you really are. Perhaps they've even had a lapse in judgement. Either way, there's never any real need to be difficult about showing your ID if you're of legal age.