Not citizenship but Argostoli police have never known so many Brits applying for a Residence Permit which they should have applied for years ago.
Could be wrong, but I seem to recall Brits don't need a Res Perm to live in Greece although a work permit is required if you intend to work... and good luck getting one of those. I heard of someone who waited three months or more. I was a bit lucky as a Greek friend went and gave the local constable a motivational speech. What was a bit galling was that every time I went the kid was sat with his feet on the desk playing with his laptop.
Whether a Res Perm is needed... it's a conversation we had on GGi a few years back, maybe Rog or someone will remember what the state of play is.
And if it's not needed now... who knows what effect Brexit will have?