Farage isn’t actually avoiding tax with a personal service company. The main reason that structure existed was to help employers avoid employer NIC. Now there’s enough rules in place to make it not worth it, and shifting the burden to the employer which is why broadcasters are now discouraging them.
Farage pays 25% on his TV income, but he can’t spend it without paying more tax. If he wants the money he earns to pay the mortgage, go on holiday, buy a boat, gift to the kids, he has to pay another 40% tax on top, which will mean he pays more tax than someone just paying 45% in the first place.
If you are earning money you don’t need, it’s a sensible structure, but it’s not really tax avoidance as you just end up with money in a pot that you can’t access without paying more tax…