I'm in England, too, and I have paid tax on crypto gains. This is more about alt trading, but worth posting as still relevant to the wider tax discussion in the UK.
I won't post the accountant I used as that would be advertising, but the position was that crypto-to-crypto trades are considered taxable events, as well as crypto-to-fiat. All of your entry and exits points have to be converted into what the fiat equivalent was at the time, plus there are additional arcane accountancy rules such as same-day, bed-and-breakfasting, pooling.
I appreciate the legislation is vague at best and open to interpretation, but I paid my crypto-to-crypto trades as capital gains. https://www.gov.uk/capital-gains-tax
It was an absolute pain as I had done a lot of trading with alts that year, and in the end I downloaded my order history from each exchange and outsourced the calculation to the accountant instead of trying to work through it myself or use one of the online services.
Nowadays I don't trade so much...