Re: Flying into UK with backpacking meals repackaged in check-in bag...
I just traveled in with a whopping 20 Mountain House meals and some other stuff. I do it all the time. They are larger than the ones here and less expensive. Plus, the selection is different, expect more curries here. And, yes, you aren’t supposed to bring meat and dairy in but there’s no declaration like you have in the US. Just don’t offer additional info at Customs, you’re just going hiking in Scotland. They may want to see your return ticket, be ready for that.
I’ve had one item confiscated in all the years, it was beef jerky that I repackaged going into Belfast on my way to Scotland.
So I would definitely would repackage in the UK and bringing your own ziplock bags (freezer type) is a must. I have found replacements but you won’t have the time for it.