I just want to highlight an an interesting parallel you've drawn here, between the "sovereignty" Ireland obtained leaving the UK, and the "sovereignty" the UK, or rather
parts of England and Wales hope to obtain by leaving the EU.
Though we define ourselves as "different" from the English, we are very much "the same" in a great many respects, and there is nobody more like us in this world than the English. In that respect England is kind of like an older brother that periodically gives us a kick but whom we tell jokes about behind their back. But we love them all the same and they us.
However, you also allude to some human rights abuses by the crown in the North, and in some respects this was a continuation of policy that had heretofore gone on in the rest of Ireland.
Do you think this is far fetched? The potato famine for a start. This was very much a political matter, and not merely a matter of a few spuds. Then there was 1916 where by far in excess the majority of fatalities were civilian and inflicted by the British army trying to regain control. Not to mention the subsequent illegal executions.
This was the backdrop against which Ireland sought independence, which seems a bit different from the narrative beneath brexit which appears to read as "something something sovereignty something something take back control".
With all that said, the UK would do well to look at how Ireland fared economically after independence. Not too well for a number of years but our eventual accession into the European Union helped to relieve that.