Plan! sit down and do a meal plan. I do soups for the weeks lunches as well. Really keeps me on track. And I eat out once a week pick steak or gammon / fillet of fish and ask for new potatoes or jacket potato instead of chips. Ask for no butter on veg or potatoes. Jobs a good'n Good luck!
Slimming world is easy. You can still eat junk food but just make better choices, for example a small bag of crisps and chocolate bar a day instead of a family size one (like me!) I lost 5lbs in two weeks which I was happy with considering I was still binge drinking every weekend.