Ha ha Corn I love the idea of an important B&Q appointment keeping you on the straight and narrow.
I agree w Broken, it's not usually as much a deal with most people as you expect if you don't order alcohol. Having said that, if you need an excuse then having to drive a babysitter home is one I've used myself in the past. I've also taken to ordering ginger ale in a large wine glass, I like the thinner glass and I seem to drink it more slowly. It's not that I want to pretend I'm drinking exactly, I just like the better quality glass and the specialness of it somehow. Weird eh?
Leftie What I would say is get your own drink in early, then hold on to it and don't finish it, then you don't get offered top ups quite so much. You could also line up something lovely and hangover impossible for yourself for the Sat am, like a 9am facial or yoga class. So the next day you can feel really good about being sober and serene. Or even just cafe breakfast out and pre-crowd Xmas shopping. I think what we really gain by not drinking is the daytime activities being fun rather than horrific. And 3 weeks is fab well done. In the early days you find you're often facing things without alcohol for the first time, but you may well find it's easier than you expect and then it feels fantaaaaastic that you've got through it.