London has 5 airports; there is also the Eurostar. If people really want to go, I'm sure they can find a way. Surely if thats too high a barrier it says something about how serious they are about founding a startup?
I am willing to create a startup on which I'm working in my free time (I need a day job to pay the bills) and personal elements made my life a bit more complicated than necessary financially-wise and I couldn't afford a trip abroad right now.
This. Personally, I think the parts of the world that will perform best in the future century and beyond are those that are the most connected. It's notable that London plus NYC, Dubai, Hong Kong, Beijing, Sydney etc are economically speaking doing extremely well - it's no co-incidence they are also very well connected.