Not sure what I've done wrong

Yeah I know ready meals etc are terrible. I make home cooked meals dependent on my days at work - if I'm in til 8pm there's no way I'm cooking when I get home. If I'm home at 5.30 - 6 then that's fine. My low cal recipes are pretty limited btw if anyone has any good'uns :-)

I THINK I'm recording my food intake directly, not sure what I'd be doing wrong there. I try to over estimate rather than under estimate.

Do you own an oven? To me, that's the best thing ever!

Here's one: get a dish that can be covered and can go into the oven, cut white fish (depending on the type of fish, the cals are between 80 to 120 per 100 g, and there's practically no fat) into rough pieces, cut roma tomatoes into rough chunks, add salt, pepper and herbs (rosemary/thyme is my favourite), stir so the seasonings are all over the ingredients, put the lid on (to keep it from drying out) and pop into a pre-heated oven at 180 to 200 C, leave for 20 min. To round it off, boil some green beans or broccoli while the dish is in the oven and voila: the whole meal (huge plateful) is usually under 350 kcal. And it takes less than 30 min to cook, at least half of which can be done on the couch :P

Ok what do I then do with my TDEE?

I'm just going to point out, I don't eat 500 cals every day, just if I feel I need to even something out. Generally it's closer to 1000 mark. It works from the old ww system when you rolled points over (although there was a minimum amount of points to eat).

TDEE - 20% is a healthy deficit that you would loose weight on slowly and sustainably. you could do a bit more if you wanted and see how it goes.

you need to look at your sugar / fat / protein intake also. thats the balancing part.