“There would be no all-island unity, as Northern Ireland could decide to – and did – remain outside the new state. An oath of allegiance was to be sworn by TDs. The British Navy would keep access to several seaports.”
Of course, some in the UK stills see Ireland as a subaltern state, and think they could be pulled out of Europe.
Also the new Irish state used the same currency as the rest of the British Isles and even decimalised in 1971 at the same time as the UK. It was only later in the 1970s that the Irish pound came to differ from the UK one.
Some Irish nationalists and republicans had long recognised that the only way an Irish state could become independent of the England was to be come dependent on some other big state, the only candidate being Germany. Which was finally consolidated when Ireland joined the Euro in 1999 while the UK stayed out.