Neutralview, I'm going to take another stab at at this one from another perspective. I'm going to ignore your question of where do they speak English and focus on where can YOU live and work in Europe and still only speak English.
In fact, there are a lot of places where you can do that and a lot of people who are doing that. Anywhere you find large groups of expats or package tourist resorts, you will find Brits living and working there without ever learning the local language and some of them get along quite well.
So really, instead of asking what is let's admit It, a dumb question, like where else in Europe do they speak English. Why not focus instead on where else in Europe could YOU live and only speak English.
Part of that is also about what you do for a living and what kind of lifestyle do you want to have or maintain. For example, there are plenty of Brits living in Spain or on Greek islands who work in a tourist related job in the season and do little or nothing in the off season. But most of them are never going to get rich that way or even manage a relatively middle class lifestyle.
So what do you you for a living and what kind of lifestyle do you want to have in another European country?