I think the UHT milk things varies a lot in different European countries (I think in general, food purchasing and shopping vary a lot) I'm in the UK and although you *can* buy UHT milk it's definitely not the norm - I have occasionally bought it (to have in the house when I got back from a holiday, for instance, or when staying on my BiL's fridge-less boat)
I think it is much more common in France (I don't like the taste, although I can live with it in coffee) an remember trying to choke down cornflakes (which my kind-hearted French hosts had purchased specially to make me feel at home) with UHT milk on them, to be polite. After the first 2 days I managed to persuade them that I would really, REALLY like to try the brioche and hot chocolate they were eating, please..
That said, I think the taste has improved in recent years. Last time I had some,I could taste the difference but it was a lot less "eeewww" than I remembered!