There are only a limited number of ways governments can deal with a large debt (such as that run up in the UK): taking via war, raising taxes, currency devaluation, or default. The first of those possibilities inspired me when, a while back, I was asked to try and come up with a good way of explaining just how large the UK’s national debt is, in a way that a normal person can understand.
Private islands around Ireland seem to be going at the moment for between US$3M and US$300,000 for 25 acres (0.1 sq km). If the UK invaded the country of Eire, threw in Northern Ireland and sold the result as a private island, it would raise:
84,421 square km x £5m per square km = £421 billion.
Selling an entire country would raise only about 1/3 of the total needed to pay back the UK national debt.