I would not waste my time telling the Britons what to do. They turned their backs on Christ, and the consequences for doing so has always been the loss of your country to foreigners. Our work needs to be to ensure we don’t do the same.
I’m not sure how the Old and New Testament theologies are supposed to mix. China has been pretty chilly about Christ and yet managed to keep a strong national identity (however vain and worldly it is). The principles would more easily carry over to churches. Allow Christ to count for little or nothing in them, and before long all you have is some kind of pan-faith kumbaya that accepts any old vision that is claimed to be about the Lord.