I just read a posting from a captain looking for a United Kindgom fleet. While I think it's important to find a fleet with members who play when you do, I like the idea of a global fleet such as Federation Fleet because we have members from arond the globe. No matter when I am cruising the stars, there's always a friendly captain "out there" with me.
So for those looking for a fleet with a lot of members in the UK, I recommend Federation Fleet. I also would recommend us to those in the US or anywhere else. Like Starfleet, we represent a diverse group of people all working together for the best possible experience.