I'm sure they operate under teh same tax regime as the rest of us- they will have the standard tax-free personal allowance, pay some at 20% and some at 40%. Having said that, they get generous expenses which are tax free and cover costs that you or I would have to fund ourselves
And that I find unethical - because the list of things that they can claim for (we now know) is far more extensive than any other self-employed person can claim.
Do as I say, not do as I do.