Actually eat healthily for £1 per day

1 calorie != 1 kcal 1000 calories == 1 kcal

All of the tables indicate the use of kcal as the unit. The fact isn't spelled out in the text, but this comment seems more like a pet peeve in terminology than an accurate criticism.

It occurs to me, that if all the parts in a conversation understand the correct meaning pedant-ism can be left aside.

I think the main weakness of the diet not listed on their weaknesses is they've made no attempt to break it down into a realistic 3x7 meal plan, because it doesn't really make one. Yeah, it's easy to put together a whole load of things cheaply that conform to predetermined values on a spreadsheet, but sometimes sum of the parts does not give you a realistic outcome.

Also, I can tell you as someone who grew up with parents that grew lots of our own fruit and veg, things like onions will survive weeks or months if they are hand-picked, strung and stored correctly but once they have been through delivery/storage/shelf stacking for a supermarket those dents a bruises start going bad quite fast regardless of your best efforts in storage so buying that far ahead may itself be a false economy.

Now if only there was consensus what is healthy eating (it changes once a decade, cyclical fashion). Fat is currently returning with a vengeance, while sugar is the killer molecule. 10 years ago a spoonful of butter was considered slightly worse than cyanide.

The amounts of protein per day is also debated as are total calories, and carb/fat ratios.

And the number of meals per day and the optimal amounts of fasts.

I think the biggest flaw is the assumption that each day must stand on its own. I'd say that its generally much cheaper to make one big meal than to try and make 3 individual meals, but there's no attempt to create large soups or chilis or something in which you CAN use fractional prices because the final product will last several days or can be frozen.