Try to cut down on carbs and sugar. (Having said that, I'm half a stone overwheight but I'm sure I'd be a lot heavier if I ate a lot of carbs and sugar).
Instead of mashed potatoes I have mashed carrots and parsnips.
I don't eat rice, and the pasta I eat I make myself from Einkorn wholemeal flour, which is an ancient grain a bit like spelt.
Sometimes I make my own bread from Allinsons einkorn blend flour, which makes a nice loaf and is more nutritious than bread made from modern wheat.
I eat quite a lot of fruit, in the form of a small fruit salad for breakfast, followed by egg, bacon and tomatoes.
I don't eat sweet biscuits, cake or crisps. If I eat biscuits at all, they're savoury, and I have them with cottage cheese and pineapple.
I wouldn't want to spend money on either Slimming World or Weightwatchers. ( I think it's got a different name now but I can't remember what it is).
I don't do a lot of exercise, but weight is about 80% diet and 20% exercise, so as long as you are moderately active you should be ok.
Good luck.