haven't a clue as to the extent of glass export, if any, that the U.K. might have had with Greece in the C19.
Individual countries within the Continent of Europe were heavily involved in home grown glass production, and it's just possible that the U.K. imported more from those sources that we exported.
If Greece didn't have the resources of wood or coal, then they may well have imported glass wares, but from countries nearer than G.B.
As mentioned, my opinion is that the manufacturing style of this piece indicates a source other than the British Isles.
The really big export route, I believe, was with the States - Ireland exported unimaginable quantities to that destination - we've had chats on that previously on the Board - volumes you'd find hard to believe.