Thanks for all the supportive comments!  I'm not going to give up this series - having read a lot of suggestions and ideas, I think what might happen next is this:
<EDITED> - this is the plan going forward:
1. Learn lessons from this one and try exactly these rules and parameters again.  ie: get back on the horse, even if only to fall off again
2. Go shopping without a budget, but with an objective to shop frugally for 3 meals 1 day - still applying the same frugality, but without an absolute limit, then when the shopping is done, review the cost of that exercise, talk about alternatives etc. ie: try to discover the boundary between 'really difficult' and 'possible'
3. Larger budget (but still tight), longer period; only 3 episodes - each 1 day, 3 meals - will be published, but at the end of Episode 3, I must show a meal plan for using and rationing what's left for the remaining days. ie: do something a bit more useful and 'realistic'*

*I still want to be cautious about the realism.  My life is pretty easy compared to some folks, and I am determined not to become a person who just blurts out glib and ultimately demeaning and insulting 'advice' to people who are suffering genuine hardship.

<Original unedited comment below>
£10 for 10 days, except I won't necessarily turn this into 10 videos each with 3 meals in them - I'll maybe do that for 3 days, and at the end, discuss meal ideas and rationing of what's left.  Or same idea with £7 for 7 days or whatever - but some longer period, with examples, and meal plans or sketches for the stuff that isn't shown in detail.
Another possibility is to go shopping without a budget, but with an objective to shop frugally for X number of meals for Y number of days - still applying the same frugality, but without an absolute limit, then when the shopping is done, review the cost of that exercise, talk about alternatives etc.

I like the idea of £7 for 7 days, which would allow things like bread/flour and bag of rice to be used throughout the week. It may be possible financially, but a challenge to combine a limited number of ingredients into all different meals.

I hope you never stop doing these challenges shrimp

I think increasing the budget is clearly the best option for future challenges. I think we've all thought "wow, he can do that with £1, I wonder how he could eat with £3 for the day" or something like that.

The specific number you are spending is not the interesting part. It's your creativity, resourcefulness and problem solving skills, and seeing what is possible for a low price.

I love these videos, please don't abandon them :)

I think this series is more important than you know. I watch these videos not just for the challenge, but for your creativity and also highlighting how difficult it is to live on a very small budget. It's so important that people with better incomes understand how life could be, if things had been different.

Please PLEASE don't give up on this series! Maybe consider doing something like "4 days on £5" so that you could buy some staples like flour, rice and fat? I truly love these budget meal challenges; they are often the highlight of my week!
PS And by all means,  include foraging!

Just increase the budget! £3 for one day, £5 for two days it doesn't matter. What we enjoy is watching your creativity and ability to create interesting meals from difficult/different circumstances. Food challenges where you overcome difficulties other than price would also be interesting eg. only a certain number of ingredients,  long shelf- life foods only, etc..

a tip for the stock:if you simmer the bones first without the vegetables, you can let them go longer then add the veg without destroying as much of the nutrients and flavours from the vegetables

Don't abandon the series!!!
I've got to admit at being embarrassed, but these sorts of videos are a lifeline for me and my family at the present time 😢

For creativity on a budget, this is informative and helpful, and the children are helping in the kitchen, so they are away from the p.c. or their phone .

Great upload.

Although it’s more work I personally would prefer more days in these challenges, I think it’s a much more interesting idea to do like a week for £10 because it unlocks some bulk items like meat or potatoes that can not only leave you more full after eating but also present some opportunities for dishes that I could try and make at home with a twist if they turn out good :)

Edit: I changed it to £10 because the comments below make sense to me. The extra money would go a long way to higher quality meats and carbs and also allow you to stay restricted with your spices and foraging without leaving you wanting more.

I used to be homeless and I've watched all of your challenge videos and I don't for one second think this is a flex on poor people lol. It's really kind that you are thinking in an informed and sensitive way but honestly don't overthink it. Yes, they're brilliant ideas for people on a budget but it's your creativity and skills that people watch you for, which can be implemented no matter how much money you have. Please don't stop making these! Ever!

I think this actually really brings the situation we’re in into perspective - I’d genuinely love to see it repeated almost identically every few months :)

My vote is option 3. Larger budget but a longer period. It's more realistic. I would suggest £3 for 3 days with a 10% contingency leeway if you find the perfect items.

Don't stop the series they are my favorite and in reality finding some solutions gives me some hope during this cost of living crisis when everything is terrible in the UK right now.

I would also encourage you to use every tool at your disposal. Take milk pots and sauce packets from the supermarket cafe and forage to your hearts content.

As for the "now what" question - increase the budget. I think you've sort of done all there is to do for the supermicro budget challenge at this point. Let's go up a little bit, where we're making economical meals but with the option to actually have some meat or fish in there.

I am not ashamed to say, I have had to live on budgets like this in the past, sometimes slightly higher, usually slightly lower, and it was always super difficult, I very regularly only ate once a day, and was always hungry.
That being said, if I'd had videos like this to go off as a sort of guideline, I wouldve faired much better.

Please dont give up on these challenges, as im sure there are people out there for which these videos are a great help.

Please don't stop the series, we need the inspiration now more than ever before. I'd love to see a £20 for 7 days for 'a couple' (2 people). I feel that most of us are happy to have a 'regular' breakfast of toast or cereal but need help finding cheap but tasty meals for lunch & suppers. Appreciate that it's a huge amount of work & maybe Jenny wouldn't want to be involved? Best wishes

Whatever you do, do not stop doing the challenge. My wife and I really enjoy your creativity with the dishes, the shopping, all of it. One of our favorite series on YouTube we watch together.

As someone in America who's been subbed for a while, please don't abandon the series. These budget videos are what got me interested and although I haven't kept up with your channel till I got this video recommended, it reminded me why your channel is awesome. Living near a bunch of main store chains, I find it impossible to even live in a budget you impose on these challenges--along with rising prices, it's great to see you make these delicate dishes with just a pound or more

Have you considered doing a challenge around one of the 'mystery' food packages that supermarkets like Morrisons and Aldi sell through food-saving apps?
It normally includes a good mix of items (bread, vegetables, sometimes packaged/chilled items like ready meals or sausages etc) that would be past their sell-by date within a few days, or that the supermarket would normally throw away for some other reason, but that are still perfectly good to eat.

"Too-good-to-go" is a good one (it's the one I use at least), and I've had a very good experience using it for restaurants etc in London, Portsmouth/Southampton, and a few other places, although I've not personally used it at a supermarket. The rule of thumb is that the food you purchase if worth about 3 times what you pay for it (about £3-4), but I've seen bags with easily over £20 of food in there.
Equally, I once heard a rumour that someone once got a bag of only spring onions, but I've never seen any proof of it.

I'd be REALLY curious to see you turn items from the box into proper meals (maybe in a similar challenge, or maybe not), or talk about how you'd plan meals out with it, or try to use all of it up, etc.
Because it's a random (if balanced) selection I feel like there's a lot of potential there for all sorts of interesting videos in the same vein as your budget challenges. Limited, but in a different sort of way.

I think I have a good idea for a challenge in the future, you have a £1 limit still, however you have it for multiple food groups. So you have £1 to spend on protein, £1 to spend on fruit, £1 to spend on carbs, and so on. You could stretch this challenge over a few days too. Perhaps half the budget if you want to do it for a day, or half the budget entirely, choice is up to you.