Why do the Celts reside where they do now?

The Celts reside in the areas they do now, because their lands were invaded and conquered by several different cultures. The Romans were the main culprit. They invaded and conquered Iberia(Spain and Portugal), in the 2nd century BC. They conquered Pannonia and Dalmatia( the Balkans region, not including Greece) in the 1st century BC. After Vercingetorix's valiant attempt to resist Roman rule in 52 BC, Gaul( France, Belgium, Switzerland, and Holland) was also added to the Empire. Britain would be somewhat strenuously held by the Romans until 390 AD, when the last of the Roman garrisons emptied to the mainland. The last invasion of Celtic lands began in 446 AD, when a Briton Chief, Vortegorn, gave land to Anglo-Saxon mercernaries, in exchange for military aid. These outsiders expanded their territories after Vortegorn's death, and after capturing London, it was apparent that they would be staying. Thus, the English nation was born, yet again at the expense of the Fathers of Europe, the Celts.