I am not sure how the UK tax code works, or what I'm looking at here (the "inside" vs "outside" part is confusing). At a glance, it looks like it wants to tax you 46% of revenue (52% of profit) at £220,000/year if you're a contractor, which (it says) is the same as earning £180,100 as a regular employee.
Those numbers don't seem particularly significant either way to me, coming from the US. Our tax brackets cap out at about 40% right now, but they used to be in the high 90%s decades prior -- and that's just the federal, and then some states have a bunch of other tax burdens on top of that. But personally, I'm economically pretty left-leaning and would prefer expanded social services rather than private wealth accumulation, so I doubt I'm representative of what the average person would consider reasonable vs excessive when it comes to taxes.
That's not really the question though. I get that a lot of people (probably most?) wouldn't pay more taxes than they have to, and frankly I can hardly fault them for that. Everything from our genes to our industrialized capitalist societies encourages in-group prioritization and selfish behaviors. That's just how this world that we've made works, and even the most fervent idealists dare not dream of making the entire world pool and share income. We just ain't built that way, and that's just opening the floodgates to insane corruption.
The more interesting question, IMO, is whether ANY of it is worth paying for collaboratively. If I could design my own tax system (and have a billion minions happily working in it...) the upper bracket would be insanely high, like 99% or some such, but there would also be a high degree of choice, per taxpayer, for some portion of their funds. Like there might be a mandatory % going to roads, defense, schools, health -- basic infrastructure, broadband -- but then each taxpayer would get to choose where the rest of it goes (say, space, basic research, the arts, land trusts, energy development, whatever). Two millionnaires would maybe each keep 50% of their income, spend 25% on basic infra, but be able to choose (within constraints) how the remaining 25% is spent. One than decide to split his 25% among various pet causes, the other might give all of hers to increase defense R&D. Basically a democratic Robin Hood, where an armed bandit takes your money and gives it to charity, but asks you, "Which charity?". Heh.
That's just me.
My question to you, as someone who goes out of their way to avoid paying taxes, is... how would you do it? Is some of it still worth it, after all the pork-barrel spending and corruption and inefficiency and bureaucracy? Should it all be private? Like take what you're doing, how would you ideally scale it up to country-level with a few million taxpayers?