Hi,
I have been offered the chance to invest in a company making reliable, small DAB radios in UK…”British designed and built, with full warrantee”
How can I find out whether or not the company is simply middle-manning them in from China?
Sounds (ignore the pun) like a bad idea.
For a while, companies are likely to be under extreme strain, because of the coronavirus and its huge economic effects. Some/many, may even go bankrupt.
With some exceptions, now is not a good time to suddenly invest in a company, you may lose all your money, in the coming future.
Given, you don't even seem to know if they are really made in the UK (or China). It sounds like you know far too little, to invest in the company.
tl;dr
Hold on to your money, and don't invest.
Also, as others have said/hinted. Whatever eventually replaces DAB, may be worth getting. But, I've heard bad things about dab radio. Such as the UK went far too early into it, and chose a terrible system, which is probably worse than the existing FM signals. E.g. Quality wise.
If they had waited, there would have been much cheaper (because others, such as the rest of Europe, would have used it, bringing the prices down and the quality up), and better solutions.
I've tried dab myself briefly, and ended up being rather disappointed with it. The sound quality was somewhat poor, and the radio seemed fiddly and a pain in the neck, to adjust/tune etc. The battery life, doesn't seem too good, either.
It should have been (my opinion), great quality (MP3 or near CD), stereo (it doesn't always seem to be, especially on cheap dab radios, which I think are mono), very good/long battery life, very cheap, very easy to use, and have much less interference/disruption to the signals.
My understanding is the dab system, offers none of what I just mentioned (even the lack of interference, although basically correct, as it is digital, is replaced by possible fading in and out signals, if I remember correctly, it was a long time ago).