The colonies had mainly long gone by the seventies. One of the last remaining, Rhodesia had been self governing since 1923 and gained full independence in 1965. They made a big success of it as we all know. I am not sure ROI did much better in the early years.What did you have in the seventies? The plebs in the colonies had figured you out and showed you the door. The two century transfer of wealth from them to London had stopped. You were a washed up, bankrupt, decrepit ex prize fighter, down on your luck and looking around for a bed for the night. The EEC showed up just before the IMF wrote a charge on the remains of the economy.
Luckily for the Toffs of the day, social media hadn’t yet been invented. If it had, there might well have been plumes of smoke over Westminster!