This can be easy!

Reading labels and noting that the calories amount is "per serving" is important. Also pay attention to the other nutrients. I know "healthier" choices are better. I have a problem with the sodium factor because of the frozen meals but have been trying to shop the "outer" aisles where the "fresh" foods are.

Only buy food that has less than 1Kcal per 1g (or in 99% of cases less than 100Kcal in 100grams - as that is what is always written on the back of packets in the UK at least)

Are you vegan (eating only fruits and vegetables -- and no nuts, no meats, no dairy, etc.)? Otherwise, I can't possibly imagine being able to actually eat anything under this plan.

therobinator - actually its not too bad, here are just a few I have at the moment

Cottage Cheese - 82 Kcal per 100g
Tandoori King Prawn Masala - 70 Kcal per 100g
Chicken in OK sauce - 83Kcal per 100g
Egg Fried Rice - 82 Kcal per 100g
Mariners Pie - 98 Kcal per 100g
Salmon Pie - 91 Kcal per 100g
Heinz Big Soup (Chicken & Veg) - 50Kcal per 100g
Ravioli (cheese & tomato) - 82Kcal per 100g

Im not saying its perfect - but definitely speeds up shopping

I am afraid some of your calorie labels may be wrong or misleading. According to MFP.
* plain white rice is 130 calories per 100G, so how can fried rice with egg be only 83?
* boneless, skinless chicken breast is 110 calories per 100 grams, so how can any chicken in any sauce be only 83?
* raw salmon is 116 calories per 100 grams, so how can a salmon pie which surely contains crust and other ingredients be only 91?

These are just a few examples I am giving in comparison to the products you've listed. I just don't want you to be led astray thinking this is an easy way out. If it's working for you, great. By all means, go with it. But the fact is that there are few foods in the world that fall into the 100 calories or less per 100 grams weight, unless we are talking strictly about fruits and vegetables and fat free dairy (no nuts, no meats, no dairy containing fat, etc).

Another factor you might want to consider is the sodium content and additives/preservatives in these processed/packaged foods you are buying. I don't know your personal level of interest in eating "clean" (if any), but it might be something to think about.

There's nothng wrong with foods that are more than 100 calories per 100 grams -- they are good for you too when you choose the right ones.

I thought that protein and carbs had 4 cals per gram and fat had 9 cals per gram. By that reasoning, you would have to be buying products that are 1 gram of substance and 3 grams of water???

Am I reading right?

This is correct! it is not 1 cal per gram