The tax is on the value, not the frequency though. So if you top up your meter with 5x £2 top ups, or 1x £10, you pay the same overall. And the rate, because it would be on everything, would be much smaller than VAT, say, so what they’d pay on currently zero-rated items like food would be offset by what they’d pay less of on VATable items like gas and clothing.
And if billionaires transfer millions to the Caymans, or buy a super yacht, they are taxed at the same rate on every pound as the guy buying his daily paper, or his morning coffee. And the interest they receive is also taxed, as are all the other ruses they use to salt money away. I’m imagining, without having done the sums, that the transaction tax could be less than 1%, if you take it on literally everything. The only way to avoid it would be to pay cash, but drawing out the cash or paying it in would also attract the tax, so unless we reverted to a cash economy, we’d collect it. And it’d probably be easier for the poor to operate a cash economy than the wealthy, so any such loopholes would be likely to help them more anyway.