London and Paris will never become competitive startup hubs for the most simplest and most important reason, the climate! Everybody loves sun and beaches!
But in the future there be a place that will concentrate and host those people ready to build this ecosystem.
It's more a culture problem Europe is facing. There may be ventures geographically descentralized that succeed but they wont be concentrated anytime soon, because there arent enough attempts and often the very comptetent people move to US.
The huge irony is Loic Le Meur, the French guy who is hosting LeWeb3, who is supposed to be working towards that purpose. Interestingly enough, his new startup is now in San Fransisco..
p.s. even if the beach is cold, I guess the sun is there and the lifestyle and life is non-stop, and must have been a catalyst in the beggining when Silicon Vally began to attract people. Anyhow, of what I now real estate was pretty cheap even 25 years ago, which must have been a very important role. Paris is already big and expensive and cloudy. London the same. Cities in Germany the same.
The people and the prices are not startup friendly.