Well they've made a complete bloody mess of this.
On my machine, I seem to now have 3 folders of ESO, my launcher starts up, no longer says anything about EU, then starts downloading the entire thing all over again.
On my missus machine, she has the 2 ESO folders, her launcher starts up, says nothing anymore about migrating for EU, then immediately throws up an error saying Already Downloading.
Total botch up. God I hate being in the EU, we're always the second class citizen as far as game companies are concerned