Most of the history of Europe is the story of one people conquering another people. Where is Gaulish spoken in France today? The Celtic Gauls were conquered by the Latins. The Gauls gave up Gaulish and adopted Latin, the language of the upper, ruling classes. Later the Germanic Franks invaded France (giving their Germanic name to the country) and the upper class Germans give up their Frankish language for that of the lower classes that they ruled, a form of Latin called French today.
Are you also going to lament the loss of either Gaulish or Frankish?
But when the Celtic Gauls invaded France about 1000 B.C., they did a pretty good job of killing off most of the pre-Indo-European people who lived there. All that is left are a few Basque in the south of France and north of Spain. The Celts practiced human sacrifice and liked to post the chopped off heads on poles. Is that how they got rid of these people?
So what happened to those pre-Indo-Europeans peoples of Britain and Ireland? Did the Welsh and Scots and Irish slaughter them like their Celtic cousins in France? Where is the language of those people who built Stonehenge? Or for that matter, where is the language that these pre-Ino-Europeans spoke in Ireland? And where are there pre-Indo-Europeans in Ireland? Were they killed off, or did they blend in with the Irish, being forced to give up their native language?
The relationships between Ireland and England are a bit more relevant than those between the Gaul and the Romans. Otherwise there would not still be the unsettled matter of Catholics vs. Protestants in Ulster, or I shouild say between Irish nationalists and Unionists. There are tens of thousands of people still alive who were young people when the Irish Free State was created, many more who can remember DeValera, who kept Ireland neutral while Britain fought for her life against Nazi Germany.