Please don't do the cereal and banana thing when you get in! Never consume sugar in the evening.
Breakfast like a king.
Lunch like a prince.
Dinner like a pauper.
Breakfast is where you need something high in protein to fill you up from the word go with some carbs. Something like scrambled eggs, grilled bacon medallions and beans. What ever it is, you want a big portion to fi you up.
Lunch is where you want the main source of carbs. And make sure it's wholemeal/wholewheat. Brown pasta, brown rice, brown bread - something like a bolognese or a chilli con carne, a homemade vegetable curry etc. Average size portion.
Evening time, you want only protein and fibre and few carbs only from veg. So again somebody like a homemade vegetable or meat curry but serve with cauliflower rice. Or grilled meats with vegetables.
If you need something to keep you going whilst at work, take boiled eggs for a snack or a protein shake with almond milk. Cut out on simple sugars, up your protein and fibre (fruit and high protein yogurt after lunch or breakfast) and you'll see a rapid difference alongside exercise.
Exercise wise, YouTube HIIT training videos - you only need to do 20-30 mins but the interval training means your heart rate is currently rising and dropping, burning rate at a quicker rate.