I was eschewing alcohol before it was cool.
Bloody hard it was, too. My school friends were the geeky types who (other than the token Muslims) were happy to drink, and even get drunk occasionally, but were mostly happy with a couple of drinks, and weren't too bothered by it - the main point of contention was that I didn't hurry up and pass my driving test. But I got fed up of having to explain myself to everyone I met who hadn't already got over it. Loud parties where you couldn't have a conversation were the worst. I'd just sit there looking bored, and people would keep asking me if I was alright, and what had I taken.
Going to university was also hard, because all the social activities in the first couple of weeks involved getting drunk. Even societies who actually 'did stuff' kicked off the term with a pub crawl or club night. Which meant everyone else got a head start on knowing each other. And again, the explaining myself over and over thing. I had more confidence to say 'no' to invitations when I knew I'd just be bored, by then.
I think it was hard because I didn't have a "good enough" reason (which basically meant anything short of driving, pregnancy or metronidazole). The association of alcohol with "having a good time" runs deep in British mainstream culture. The best policy seems to be to lie.
Good luck to them, I say.