You do know, Call, don't you that most of our 'money' doesn't actually exist in any tangible form? It's just a series of credits and debits on bank computers. Your bank doesn't hold any tangible form of money (apart from some cash, which people like to use for some things, but is increasingly used less and less in financial transactions), it mainly has figures on a computer. When it 'lends' money it tends to create it, under licence from the Bank of England, it doesn't have to have taken in enough in deposits to cover the loan.
Our income tax isn't the only source of 'income' the government has. It takes corporation tax from companies, tax on dividends and VAT from companies and consumers. It also has income from sundries like the Crown Estates. So the little pie chart on your tax return is a little bit of fiction really. At best it probably describes the theoretical apportionment of income tax receipts to various usages, but it doesn't account for all the other sources of government income allocated to them, or give any hint that the government itself, via the Bank of England, is able to 'create' money if it needs to (see quantitative easing). It does, though, deliberately or not, I don't know, give the impression that your tax is needed to pay for government expenditure amd is its only source of income. Which is handy for the government when it insists that it 'can't afford' to fund the NHS, or Education, or whatever.
Which doesn't mean to say that we don't need to pay our taxes. If we didn't pay any tax and the government just kept on creating money to cover its spending needs inflation would be rampant because there would be far too much 'money' around.
P.S The thing about computer generated credits and debits was confirmed to me by a friend who held a very senior position in a well known UK bank.