Not so! What you say is true for a country that has not achieved monetary sovereignty, or for a country who has given it up (like the Eurozone countries), but the UK, like the US, Japan, Australia, New Zealand, etc. originate their own currency (only issuing bonds in their own currency, which their own central bank issues, and not having any pegs to other currencies).

There is nothing that the private sector can afford in the UK that the UK Government can not afford!