Thank you so much everyone for the great advice. I wish I could just attend the ceremony but the bride is my girlfriend's step-sister so I'm at the top table with the family, many of whom enjoy a drink or five lol. You're right though, I will look for the people who are not drunk and stick near to them. My girlfriend isn't going to drink so that's at least one person, although she says she will find it hard not to drink so I feel kind of guilty about that.
Bunny - oddly enough, I think accidentally getting my glass filled and somehow managing to accidentally drink it is one of my fears, which I know sounds daft but it's there in the back of my mind despite rational me knowing I have full control over my limbs and mouth lol. I had never thought of something as simple as just turning the glass face down! Thank you