I need some help to get my food budget down, but it needs to accomodate a very hungry 9 year old

[saltire]

at the amount of food my DSes, especially DS1, is eating. DS1 eats huge adult size portions of food. My food bills have gone from £50 - £60 a week to alomst £100. A box of 48 weetabix lasts under a week, 1 1/2 loaves of bread a day, 12 pints of milk a week.
We can't afford to sepnd so much on food, I'm not working at the minute and I'm trying to budget with the food, have shopped at Lidl or Aldi, but each time it was high totals at the end. last night for example DS1 (he's9) had 4 slices of roast beef, 4 yorkshire puddings, 2 roast potatoes, mashed potatoes, broccoli and carrots. He had a smallish plate full to start with but kept asking for more. he ate twice what I had. Then he had 2 portions of apple crumble, follwed by a banana, then 2 slices of bread because he was still hungry. He had toast and a banan at bed time, because he has been waking hungry, yet still had 4 weetabix and 4 slices of toast this morning.
Is there any way I can get my food budget down whilst not starving DS1 and 2?
I do menu plan, but it all goes out the window as DS1 just asks for more!
Am nipping off for a shower, will check back soon

What about starting evening meals with soup - is an old fashioned way of filling everyone up cheaply before you move onto the more expensive main option!

If it's any consolation my mum says my brother was exactly the same at about 10 - ate for Scotland and was skinny as a rake. I know that at 9 I once ate 12 yorkshire puddings at a sitting with a roast dinner, and i was so skinny you would not believe it....if only i still could. we were on the go physically all the time, so rekcon that's why we ate so much.

we also used to get given porridge for brekkie as it filled us up, then a slice of my mums home made bread which was so heavily wholemeal you could only eat a slice anyway. Weetabix is not THAT filling......wel I don't think so anyway.