Thanks, all. I should really have said that the U is actually mostly halfway between F and V sounds. That's hard for English-speakers to distinguish.
Greek people are endlessly forgiving about these things, but it's nice to get it right.
I find the letter G a bit of a problem. Sometimes it's hard, sometimes it's almost an H sound. For example, England in Greek is Agglia and that's fairly hard with two gammas - Agg -LEE-a.
But the real name of the village is, of course, not San Stefanos but Agios Stefanos, and it seems to be much softer - AH-yee-oss STAY-fan-oss.
I'm sure Tredegar Boy will be able to help with Welsh, which has similar traps!