Your not comparing like with like - simple as that.
If you want access to an enormous selection of world class restaurants, theatres, museums, night life, shopping and more then London's a good place to be.
If you want the opportunity to work for some of the worlds biggest and most successful companies in an environment where you can really demonstrate your worth and where you can expect to be rewarded handsomely for it then London's a good place to be.
If you want to able to fly direct to nearly any place on the planet then London's a good place to be.
If you want to top up your tan and drink Keo then London's not a good place to be ......
As far as living / working in Cyprus is concerned then you need to look at what you want / need and hope to gain from moving here.
If your the boss, who cares if you speak Greek? Hire somebody to do it for you.
If your skills are in high demand / highly specialised then I doubt you will need to speak Greek and you can also expect to be well paid.
If you fit into neither category think long and hard about it, a crap job is a crap job and when the thermometer hits 40 it'll feel even crappier.