If you want to sell worldwide, I wouldn't use .london extension. This extension specifically tells Google (and buyers) that you are local to London. Sometimes I understand why Aussies or Americans would order from .co.uk but usually only if it's our last choice, honestly. So why would we order from a .london if there's ANY other choice?
You could run a .com or .net as your main domain and then run .london geotargeted to your UK audience. I think it's a mistake to use it globally.