It's the same everywhere, and even China is copying the model. Housing is a fixed asset and everyone needs one, so the moment you allow people to borrow to buy and let then the renters are stuck and the house prices soar.

The reason it's the same everywhere is that this model magically creates "growth" and "wealth". My house is worth £100K. House prices increase. So now there is more wealth in the economy (there isn't, but economists think there is). Now it is worth £120K.

I remortgage and - voila! I have £20K to spend. Now I can spend that extending or upgrading my house, now the plumber and decorator have jobs, and Amazon or whoever sell new curtains, and everyone is happy.

This is a particularly useful model to follow if you don't actually produce any real wealth, because you exported all your manufacturing jobs abroad and whilst we like to pretend an economy can run on services, in reality we run a massive trade deficit and are selling off assets to pay for it (guess which assets we sell --- we export house ownership to rent seekers from abroad! My last landlords were based in China and I live in the UK! The system works)

But even economists are aware of the difference between wealth and value : you are describing inflation.

Why were you allowed to / it was a good idea to remortgage under ~20% inflation ?

I think inflation is when the value of money drops ie it can buy less of everything. But this is simply the cost of one asset rising.