Assume 1 pound of weight loss per 100 miles of cycling, provided that you don't take in many extra calories to fuel that! It might be a bit more or a bit less but it won't be too far out.
Restrict yourself to 1 take-away a week maximum and don't take the opportunity to completely pig out when you do have one! Cut the booze intake right down. A maximum of 3 or 4 pints once or twice a week, preferably less.
Greatly restrict junky snacks, preferably eliminate them.
If I ride 100 miles and drink no more than 5 pints of beer in a week, I lose about 2.5 pounds. If I cut the beer out altogether and do more than 100 miles, I can lose 3 pounds in a week. I'm not currently doing that, but I've done it in the past a couple of times and lost 3 stone in less than 6 months.
I don't have a problem with food. I eat lost of steamed vegetables, salads, tuna, low fat cottage cheese and so on. I don't eat meat, and can't have bread or full fat cheese in the house because I am fatally attracted to them! (Toasted cheese sandwiches and the like are treats at cafe stops on forum rides!)