My advice is to take one step at a time.
Don't go from one extreme to the other and fail; instead start with the chocolate problem and deal with it. Stop buying it today. Have a cup of coffee instead. Don't worry about eating tinned soup, eggs on toast, etc they won't do you half as much harm as the chocolate.
Instead buy some interesting fruit (ready pealed and chopped mango/pineapple or some soft yellow plums for example) and some greek yoghurt and replace the choclate fixes for more natural sugar. And have another cup of coffee.
Then and only then can you start eating more healthily in other areas. You'll feel lighter and more motivated once you've ditched the chocolate.
Find a positive attitude about it and reward yourself with things other than chocolate, like a bunch of daffs or a new lipstick.
Then when you'll feeling grett you'll find yourself looking for new menus and things you can eat on the go which are healthier. Good luck