Questions about WW2 Ration diet

I have questions about this so please bear with me. I take in students temporarily between feb and june to make some extra money. It is usually very lucrative but I'd like to slash my food bill further and read about this Ration diet after seeing the series on TV awhile ago.
I need to provide brekfast, lunch and dinner for 3 children for between 3 and 4 nights at a time. Currently I provide cereals (tesco's value or aldi/lidl specials) toast and choc spread (usually tesco value or lidl) Lidl bread rolls are 29p for 12, ham or chicken for sandwhiches, value yogs, value cake (26p mini rolls or 1.19 for 3 madiera slab cakes) crisps and cartons of drink + fruit. I do pasta based meals and simple puddings. Any advice pls. BTW there are 3 of us already and I usually spend £50-60 per week on food shoppping when I have the students. Is this too much, about right? Can I cut it further?