While I get your offer, I wonder on the economics.
You need website, payment system, office, way of working with suppliers and customers, a chilled delivery van. That is £'000s to set up.
Say you can buy all this small, fresh premium stuff for £20. (I suspect more...)
But you have to shop them individually and freshly, and deliver. So £20 travel.
Then the shop/campsite want a cut, so add another £10 and it is sale or return and return on fresh stuff is wasted so that is now £40 down.
You need to charge profit on top of direct costs, so suggest £10 per box.
Each box then retails at £50+
But you did not sell one box and that wipes profit from the 4 boxes you did sell due to sale or return.
And that is before you pay for the office, ordering system, van, website, phone, laptop etc.
To make a reasonable income from this you would need what, daily sales that lead to £300 profit a day, half of which is overheads and half of which is income for you. That is 150-300 boxes a day sold. Maybe you can find 30 local campsites and sell 8-12 boxes a day to each site?
And of course this is seasonal. And everyone wants the boxes on Monday, Friday, Saturday and Sunday.
So no weekends again for you and your family.
And then a supplier sells out of burgers on the day you have orders for 400 burgers...or forgets to bake your buns...or the salad is crap.
So lets say you work flat out 4-5 days per week for 3 months of the year and 3 months at 'meh' levels. You would be lucky to clear £10k gross for those 6 months, minus of course taxation.
I may of course be wrong, but this sounds like a hounding for nothing....