I was wondering why someplace in Greece had coins that made it look like part of the British Commonwealth, so I did a bit of digging, and here is the thumbnail history for the Ionian Islands, a group of 7 islands that lie off the NW coast of Greece, of which Corfu is the best known.
Historically the islands were Greek, then part of the Roman and Byzantine empires (nothing out of the ordinary yet), but as the Byzantine empire weakened in the 13th century, the ascending Venetian Republic took control of the islands, as they were useful way stations for the Venetians' Mediterranean trade routes.
They remained under Venetian control (despite attempts by the Ottoman Empire, which had taken Greece in the 1450s), until the Venetian Republic was conquered by Napoleon in 1797. In 1809-10, the British won naval battles over Napoleon in the Ionian Islands, and in the 1815 Peace of Paris, the British retained control of the islands as a protectorate (mainland Greece was still part of the Ottoman empire).
Greece obtained its independence form the Ottoman empire in 1830. And in 1864, Britain returned the islands to Greece.
From a modern numismatic viewpoint, there are some very rare counterstamped issues from the 18th century (KM20-25, 30, 50 and 60 paras counterstamped on Spain, Naples & Sicily issues), and the issues iunder the British protectorate (dated between 1819-1862), of which the 1 Lepton piece is the most common.