Control weight with diet.
Control fitness with exercise.
Overly-simplistic, and obviously exercise will boost weight loss, but it's all about looking at the situation as a whole, rather than thinking about the various components in isolation.
Like you, my biggest nemesis is the booze. Since starting cycling, I've lost around 2.5 stone, but I've now reached the stage where I've pretty much plateau'd. I eat pretty well, but I'm over-fond of a few beers at the weekend and it's all dead calories. I eat well/healthily for the majority of the time, but there comes a point where you have to decide where your priorities lie. Losing weight is an endurance event: If you want to do it, you have to be prepared to be hungry!