Austerity is not a political decision it is an economic one. It's like one of us living high on the hog on our credit cards, then borrowing to consolidate and still using the credit cards.....it's then either Bankruptcy or some serious austerity measure to save us from economic disaster.
Your analogy is completely false, Allyg. National economies are not like household or personal economies. This is just a myth promulgated by one set of economic theorists which has gained traction because it's an analogy which resonates with most people and has proved useful to our governments when they wish to shrink the state in favour of private enterprise. Though, as mostlyharmless is pointing out, it doesn't really seem to work as cutting spending in one area, housing provision, has just increased spending on welfare, housing benefits.
Households and individuals have a finite amount of money. They cannot spend more than they have unless they are prepared to take on debt which they very likely cannot afford to repay (or even service in many cases). Governments which control their own sovereign currency are not confined to a finite amount of money. They were in the old days of currency being pegged to the gold standard but that was abolished in the early 1970s. They are not confined to a finite amount now. Nor are they actually obliged to borrow from anyone to finance their spending (though they still do to a certain extent by issuing government bonds). The past decade has seen quite extensive use of Quantitative Easing (QE) whereby some £340+ billion has been created by the Bank of England, initially to cushion the economy against the international banking crisis of 2007/8 and latterly to prop up the pound when it fell sharply after the Brexit vote. The objective of QE was to put money into the economy to keep it 'working'. Unfortunately it went mostly into the 'wrong' economy. Instead of going into the 'real', everyday economy (the one that you and I and most people exist in) through investment in infrastructure and new businesses (creating jobs and purchases which keep money moving around the economy and eventually returning to the treasury through taxation) much of it ended up in the financial markets, inflating bond and equity prices and making a lot of already wealthy people even wealthier.
We know that 'trickle down' doesn't really work. Wealthy people tend, on the whole, to put their money to work in the financial markets to make more money and then aim to pay as little tax on it as possible by squirrelling it away in tax havens. They may spend a bit more on high end goods and services but not enough to make a difference for most workers or businesses.
I know that the argument against putting more money into the economy is the danger of inflation but some causes of inflation, such as increased cost of oil and raw materials, are beyond the control of any government as they are sold in the global market. There comes a point where restricting the money available in the 'real' market puts the cost of goods and services dependent on global market prices beyond the reach of 'ordinary' people and the businesses supplying these to the domestic market suffer loss of income which leads to cutting jobs and lessening the tax take from people's earnings and taxes on profits. Which makes no sense whatsoever.