You didn't put all this weight on overnight and you won't lose it overnight either. You've made a great start in focusing on what you are currently eating and deciding to improve on it. Pat yourself on the back for that.
If you can, to get you started join an online or real life club
This is a day by day journey. You will have healthy days and some bad days. The idea is to have more healthy days . Get back on the horse and keep going. Apparently it takes 20 days to learn a new habit - like drinking more water.
I found it was hard in the first weeks because it was all about menu planning and thinking about shopping and cooking for food was quite overwhelming, plus trying to make the rest of the household get on board - which literally just made me hungry all the time. I wanted to stop thinking about it! Just try to keep moving in the right direction and accept that you will have slip-ups on the way but you will keep going. Build up some cards with meals that work for you... so you don't have to think about it so much.
But if you decide it's more about health, then its not so hard to start slow, eg find five breakfasts you can live with, write them down and shop for them. Look up overnight oats. If you like full English, how can you make it healthier? Eggs and sausages (Quorn would be lower fat?) Low carb/low sugar beans? Grilled Tomatoes or Grilled Mushrooms? if you had a nice breakfast to start the day, you'd feel more satisfied.
Try new cooking methods and new recipes. There are so many quick healthy meal prep ideas on Instagram/you Tube - (longer) . its less time reading and pondering as they are all videos... and I've had a lot of good ideas from this. Decide to make one of them at least once a week.. and put it on your menu card. Once you've told yourself its OK to do a bit of tedious tracking for the first few weeks, you will get used to it and it won't be so intense.
Don't let this put you off socialising. You are trying to get away from the idea of diet as punishment or deprivation. If your food is fine the majority of the time, you can get away with going out for a meal. Just watch it a bit. but don't go on about it in public or you will feel under a microscope. You don't have to have salad every time you are out. Everything is in moderation so that its sustainable.
Keep supportive people around you. (which is why a club/group is a great idea) But If anyone is a weight nag, or makes you feel bad, don't tell them you are dieting, shut them down on conversations as they can derail you and just say I'm focusing on improving my health every day and change the subject.
Snacks; You seem to want a lot of snacks. So find ones that are good for you. that you can live with, write it down, shop for them etc. Think about why you want them/ eat them. Is it comfort eating? or boredom? what can you do to alleviate that.
Drinks - Fizzy drinks are not very good for you long term. Sparkling water? Flavoured with fruit juice and lots of ice, mint, lemon etc. Cut down on Alcohol - Drink Aware app is very good for this and I found it very easy to use.
The more water you drink. The less thirsty you are and the less you will need the fizzy drinks. I tried having white wine spritzers when out as it made the drink last longer and was thirst quenching and so cut down the amount of alcohol.. also alternating with a soft drink.
Exercise At 17 stone, I think you should start simply with things like walking until you lose weight, to protect your joints. Wear good trainers. Week 1 just find some quick 5 - 15-minute walks near you daily and even if you are busy, squeeze them in. You can build up and go longer walks when you have time. Earphones in. It's still nice light weather ATM. Wear a cagool and go even if its raining. Diabetics are advised to do this after food so that's a good time too. Find a good Stretching programme on Insta or You Tube that you can do first thing. Swimming is excellent, even if its just a quick swim to start with. Cycling, also kinder to your joints. Once you get started you can build up.
You sound quite motivated and that's the best start. Best of luck.