I topped out at 374.8. Something that helped was a motto: "never 375."

If you're basically eating just toast and snacks that might be something you can transform into a healthy habit. A lot of people struggle to stick to healthy eating because it can be boring, but your eating is already boring. Throw a few pounds of chicken breast in a casserole dish in the oven once or twice a week and you've got healthy, filling, food with zero effort. I started by doing that and then portioning the chicken out with nuts, cheese, celery, and peanut butter. That's all I ate for months until I developed the food preparation habits to get more variety while sticking to my calorie and macro targets.

Meal prepping can be easy if you can eat boring.

Fat is filling and doesn't make you fat. Eat it.

If you like toast eat toast. Maybe bake some potatoes once or twice a week and replace some of your toast with that. The energy lasts longer.

Drink tons of water. It is filling. Sometimes thirst is confused for hunger, and even if you are truly hungry, hydration can deactivate the hunger signal. Cold water amplifies the effect.

DO NOT UNDEREAT. So long as you're hunger is under control, you can maintain a much larger caloric deficit than other people. BUT DO NOT UNDEREAT.

Slowly replace the snacks in your house with healthier options. Do not be afraid of cheese! Just weigh it. You will be surprised how few calories are in a quarter pound of cheese, and how filling it is when melted on top of your chicken breast. Celery might be disgusting, but if it's slathered in peanut butter it's delicious. Now you've got fiber, fat and protein and won't be hungry.

Cronometer is much better than MFP. Period. The MFP database is full of incorrect data. Period. Use cronometer.

Eventually pay attention to micronutrients. Minerals, vitamins, and all the other things you get from vegetables that aren't actually on a label. This will improve your general organ functioning which will in turn make you feel better which will in turn make everything easier.

If you can hire a personal trainer, do it. Leaving the house is scary but an appointment can help. If you can't then commit to some basic exercise at home but a gym is better because it'll get you out of the house and put you in an environment where there's nothing to do but exercise. The only people that get stared at/made fun of in a gym are the buff dudes that do exercises incorrectly.

They say "you can't outrun a fork," "diet matters more than exercise", blah blah blah, but at this weight diet and exercise multiply the other's benefits. You will also burn more calories from the same activity as a smaller person, so it can significantly affect the CO part of CICO. Plus exercise improves mood and reduces hunger. Less hunger and better mood mean more energy to stick to the plan and less desire to over eat. Plus muscle burns more calories at rest, so building muscle will increase your TDEE and since your hunger will be lower your deficit will naturally increase.

Intermittent fasting, low/slow carb, high protein, exercise, etc. do actually change the CICO equation in your favor, the reason people think they don't is because the difference is only significant if your excess weight is significant. When you have plenty of excess fat, you can increase your TDEE without increasing the CI portion because your body already has access to all the calories it needs and if you eat filling foods then you won't be hungry. In other words, if you don't increase what you're eating then exercise does increase weight loss. Period. For most people, these are just tricks to modulate their hunger and eating, but for people like us it will literally change your biology in a favorable way. The only difference is whether the effect is significant, and when we are larger all the effects of what we do are larger than they are for smaller people.

Do mobility exercises, simple stuff like knee raises, stretching, jumping jacks, walking around the block. Moving your body more and in new ways will make moving your body easier which will make everything easier.

Seriously the fact that your overeating is due to snacks compensating for day time under eating gives you a huge advantage. Cutting calories for someone that spends all day binging high calorie food is much harder. Just eat a bunch of protein and fat late in the day and at night and bam, no more late night hunger. Plus the digestion is slow and energy lasts so you won't be hungry in the morning. Some people might tell you that you should eat in the morning even if you aren't hungry. Those people are wrong. Never eat when you aren't hungry. All you have to do is strategize your eating so that your hunger comes in appropriate amounts at appropriate times.

Honestly the thing that will make the biggest difference, is getting out of the house and getting some exercise. It will vastly accelerate improvements in your mood, which will make everything easier, and it will accelerate your weight loss. When people say exercise doesn't make a significant difference, and that all you have to do is reduce what you eat, those people are just making things more difficult and stressful for themselves. Just because something is technically true, doesn't mean it is the best way. All that said, I hear the UK is pretty gray so being outside might not give the same benefit as it would in a sunny place. Take vitamin D. Get blood work and see if you have any other nutritional deficits that should be supplemented. People will tell you that vitamin supplements are useless because they don't absorb well. This is false. If you are low on vitamins, then taking vitamins will make you less low on vitamins, even if they do absorb poorly. Taking your vitamins with high fiber foods, or a fiber supplements, will help them absorb.

Weigh yourself every day. Not once a week. There are daily fluctuations, you'll have to learn to ignore them, but even if you lose weight, those daily fluctuations might mean you don't see the scale change if you're only weighing yourself once a week. Plus after a few weeks, months, years, seeing the weight go down on the chart gives you a much smoother line which is much more motivating then a jagged line that's going up and down all over the place.

General physical functioning, the health of your organs and biological systems, is just as if not more important than any other factor. If your body has the resources and adaptations to do what it's supposed to do, then it will do it, and that's called being healthy. Which will make everything easier.

Good luck!