I wouldn't bother if this is something your paying for. If this is a fad diet then, it's like what you get in them magazines. Don't go on a diet either that's bad because it's like getting on a bus, you have to get off at some point, chances are you'll pack pounds on if you 'ditch' it or 'finsh' and eat as normal.
The main areas where I'd be concerned are FAT, ALCOHOL and SUGAR
FAT -- these are things like chippys or fried foods. I'm sure you can see these giving you a bit of a belly. Try cooking your own food and boiling/steaming/grilling it.
ALCOHOL -- okay so every friday or saturday you and your mates drink 10-20 pints and get drunk ... consider the amount of calories (150-200) in each single pint. Try something like a spirit straight, insted.
SUGAR -- drink tea and/or coffee? fill them with sugar? Either don't use suga, switch to a sweetener or reduce the sugar amounts. Avoid sweets and fizzy drinks loaded in sugar.
Check the amount of calories in your food. Split your meals up insted of having big mad meals, try having little ones through out the day (5/6)
Try eating more whole foods like pasta, bread and potatos so they'll suppress hunger for longer.
You wanna be making these changes PERMANTLY insted of 'just for a few months'
Don't starve yourself either ... your metabolism will slow and you'll stop burning fat as quick.
Okay, now is the hard part. Exercise, okay SO on one end you have less food coming in now you wanna push the weight out. Do some cardio for about 45-60 minutes maybe. Bikes are great because you can transport to your city centre or somewhere. Got a park near, try jogging there.
DON'T stop and say, "I aint losing weight my stomach is still flabby, I'll leave it" ... IIRC the body decides where the weight will come from in cardio so you might not notice weight loss in THIS AREA, same goes for eating, if you stuff yourself it might hit a certain area and then work around.
Drink water if you aint doing already.