I don't think that's true at all. You be taking payment by credit card, which doesn't require you to have any local presence.
I think your bigger risk is that you get a judgement made against you by a UK court, which a court that has jurisdiction over you is willing to enforce. I'm not sure under what circumstances that is the case, but I believe that it being the case with libel judgements has been an issue for a while (since plaintiffs can 'forum shop').
But you're offering an online product, plus you are taking money from people from all over the world, whose governments have different regulations and points of view, your own business charges differently for different countries, and credit card providers are bound to different fees and/or extra charges for international transactions.
It's not a simple solution.
I broadcast radio from my country, according to the rules of my country. If you tune in, and your country doesn't like it, they can enforce on you or broadcast something else on the same frequency if that's allowed by their rules.
This is quite obviously incorrect. I am a UK citizen, but live in the US. No company needs a UK presence to collect money from me.
But we're clearly far beyond that here.
Company A sells cryptocurrency in country A. Company B is a payment processor in country B. You in country A go to the country B merchant's website and enter your card info to buy something. Your card gets charged by company A to buy cryptocurrency, the merchant gets the money through company B and the transfer of cryptocurrency from company A to company B happens in software on a server somewhere and the user doesn't have to do anything.
Why is this either not happening or not sufficient?
We are building exactly this at Intercoin. I hate that most of crypto is zero-sum games. https://intercoin.org/currencies.pdf
Also Stripe is launching Tempo blockchain, USDC is launching Arc blockchain. Cool things are coming!
EDIT: I clicked on the PDF out of a sense of good faith interest and curiosity and I regret it. I hope you find something else to do.
You only have to have presence in the UK if you do some larger-scale commercial activity there (like X/Twitter), but of course you can easily sell goods and services to UK citizens without all that. But sites like 4cahn and SaSu don't even sell anything at all.
Please downvote the parent comment into oblivion.