Got it - wasn’t sure because of your profile name ir perhaps burn your greek passport.
I had a greek colleague and i told him once, let me guess, you’re going to make your money in CH and then retire in Greece living like a king. He smiled and said absolutely.
I tries convinxing my wife of such a model but she is swiss so that settled it, plus i dont feel at home anymore in my home country (havng been gone 20+ years and lived all over the world) and i appreciate all the benefits of switzerland.
I’d go (back) to the UK, love the place, understand it and the people, and never felt like a foreigner there. Probably helps I had an English nanny as a toddler, studied and worked there, and still work for a UK company so go there all the time since 2000.
Edit: I feel that VERY few people are fine to be permanently away from the birthplace. I think the US is among few places which really assimilates foreigners. No country is special, and simultaneously they are all special to someone!
I’d go (back) to the UK, love the place, understand it and the people, and never felt like a foreigner there. Probably helps I had an English nanny as a toddler, studied and worked there, and still work for a UK company so go there all the time since 2000.
Edit: I feel that VERY few people are fine to be permanently away from the birthplace. I think the US is among few places which really assimilates foreigners. No country is special, and simultaneously they are all special to someone!
Edit 2: my plan, to the letter!
Greece - I get that entirely: relaxed lifestyle, great food, enjoyable climate, culture, mountaints to med, etc. plus if you speak Greek even more… and on top financially it’s easier than Switzerland.
UK - really surprised me. I have heard from so many Brits that they have been saying the country in decline for years now and they’re either not returning or regret not leaving or plan to leave. I’m a big fan of London, but that’s a different world.
Pretty stark contrast between your two options but can’t argue at all with your Greece plan!
Our neighbors have their main residence in another similar southern european country. What for us is our dream home, for our neighbours is just a tax/healthcare pied a terre in Switzerland 
Greece, relaxed? Not at all! Nervous, constantly angry people. Don’t mix being unreliable with relaxed. Greek weather is too hot in the summer, it’s changed a lot, now it becomes very unpleasant. The food is indeed god tier, I’d only put the Italians on par, even maybe better - for my tastes at least! Sea and mountain are great indeed. But it’s also the familiarity, experiences, people. Something snapped and suddenly “the abroad” became increasingly unbearable. That’s the broader point: many many places have great food, nature, history, culture, however somehow I stopped being interested!
The people for which “not too bad” means “I’m well”? Professional whingers. Multiple years of bad governing by the Tories are to blame in a large part, real shame. Middle class in the UK is fcUKed, society in shambles, ungovernable. How many PMs have they changed the last 10 years? 5-6? Now Starmer is likely going to fall soon, I don’t believe he did anything wrong, especially with the mess he received.
But…I love the place and the people.
Sorry for less coherent writing, all on the phone with one hand 