Hi, user 
The actual food you listed is very little - do you really have no protein or healthy fats at breakfast or lunch ?
You don't seem to be getting enough nourishment, but instead getting a high % of your calories from calorie-dense junk like "lots of cake and chocolate and biscuits"
So, I recommend changing the type of food you eat, not reducing total calories
In fact, without junk, you could eat a greater volume of food, while getting healthier
All calories are not equal, certainly not when it comes to health
Sugar and junky carbs pile on visceral fat, i.e. the dangerous kind around the internal organs, which interferes with their functioning.
Studies have shown a clear link to the % sugar consumed - not just the total weekly calories - and diabetes risk.
Excess alcohol adds visceral fat too, so cut down to NHS alcohol levels if you are a drinker
I recommend:
Have a proper breakfast, lunch, tea and supper - each with protein and healthy fats, healthy carbs - no snacks between, even healthier ones.
Cut out the junk and that should help a lot.
e.g.
breakfast: porridge with fruit / wholegrain or rye toast with egg or pnut butter
lunch: add a good portion fish / chicken / steak strips to your salad and drizzle with olive oil
tea: full-fat Greek yoghurt with berries
supper: reduce your huge meal, since you are eating 3 other meals
and finish eating at least 3 hours before bedtime - regualrly having late meals has been shown to increase health risks
Have a least a brisk daily walk if you can, because exercise also reduces T2 risk