In terms of the clubbing experience, it depends on the people you hang out with. The first few friends that I made aren't particularly massive drinkers but we still have a good time. Whilst it is true that some people do get drunk and hook up, this is not to say everyone is like this, and if you aren't interested, you don't have to do this too. There are normally good deals for drinks, especially on student nights or clubs at the student union.
In terms of Freshers Week as a whole, not everything is clubbing. If you try it once and don't enjoy it, there are other types of events you could attend. When I was there, they had dinners, film nights, bowling and games night. It is all about finding your interests.