It's a British Overseas Territory, a lasting remnant of British imperialism in the Middle East. So, these refugees landed on sovereign UK territory. As per the OP article : "It is believed to be the first time during the current Mediterranean migrant crisis that people have arrived on UK sovereign territory."

More background info here:

"Akrotiri and Dhekelia (Greek: ?????ή?? ??? ???έ????, Akrotiri kai Dekeleia; Turkish: Ağrotur ve Dikelya), officially the Sovereign Base Areas of Akrotiri and Dhekelia, is a British Overseas Territory on the island of Cyprus. The Areas, which include bases and other land, were retained by the British, under the 1960 treaty of independence, agreed and signed by the United Kingdom, Greece, Turkey and representatives from the Greek and Turkish Cypriot communities, which granted independence to the Crown colony of Cyprus. The territory serves an important role as a station for Signals Intelligence and provides a vital strategic part of the United Kingdom communications gathering and monitoring network in the Mediterranean and the Middle East."

https://en.wikipedia.org/wiki/Akrotiri_and_Dhekelia

Thanks for the extra info, I find the intricacies of colonial relics and weird sovereign bits and pieces of former empires like this fascinating to read about.

reverberates today. What a mixed up thing it is. Perhaps inevitable, given European history, but what a mixed bag.