I know the NHS is funded mainly from taxation although we are led to believe NI contributions fund it.
No, we've been told for decades that it's funded from taxation, but it isn't.
Taxation just doesn't fund spending. We know very well (or should) that the government can issue money when it pleases, without having to tax to fund it or 'borrow' it from anywhere. We have a sovereign currency, we can do this and have done for a long time. If the government, via the Bak of England, hadn't been issuing more money into the economy We would all be scrabbling round for an ever diminishing share of of a finite pot as our population increases.
Since the Global Financial Crisis in 2008 there has been some £450 billion issued in the form of Quantitative Easing by the BoE. Specifically to save the banks in the GFC, to bolster the falling pound after Brexit vote and to pay for the costs of the covid pandemic.
Has this caused inflation (the current inflation has a number of causes, but it certainly isn't caused by too much money in the economy)? No, it hasn't.
Has it meant increased taxation to 'repay' it since 2008? No, it hasn't.
The current tax increases are, inexplicably, damaging to the economy and economically illiterate.
If there was the political will a large injection of money into the Health and Social Care services wold be really good for the economy; so much private business would benefit from it; from NHS suppliers to the local shops and businesses where the NHS employees spend their wages. And most of it is taxed back, you can't do much in this world without paying a tax of some kind or another.
If we, the populace, could take this on board then we could be thinking completely differently about the funding of public services (and why most of the issued money ends up in the hands of the already very rich, like the covid money).
Taxation has a number of useful functions and, of course, the revenue from it helps to ensure that the government doesn't have to issue more and more money, but funding spending is not one of them.