Mumsnet frowns upon anyone who has more than a small sherry at Christmas or who has anything other than the most uptight and professional relationship with their colleagues.
In my experience, this isn't really the way the real world works, however. And LOL at people who think nurses and doctors need to 'set an example' by not letting their hair down at a Christmas party. You're a human being and you can behave like any other human being.
In reality, go to your Christmas party and if everyone else is getting hammered, feel free to join in. But just judge the mood on the day! If it doesn't seem like a boozy night, you don't want to be the only one getting drunk, but if everyone gets tipsy, it's absolutely fine.
I had my work Christmas meal/drinks this week. Nobody was ridiculously drunk - no throwing up, falling over or having fights - but most of the people who stayed out after the meal for more drinks were certainly tipsy, including me and including our boss, who was generously filling everyone's glasses for most of the evening. We had a good evening with a lot of laughter, had a few conversations we definitely wouldn't have had in the office, and had mildly sore heads the next day.