"British tech firms gained more venture capital investment in total than Germany, France, Spain and Ireland combined."

This is more to do with Brexit than really competing with Silicon Valley. London is the destination of choice for rich people trying to get their money the covfefe out of Dodge before the Euro and the EU collapse.

London is still in the EU at the moment, but after January 31, the rules they have been operating by go out the window. Everything in the UK has to be re-negotiated with the EU, so it's very unclear what the new rules will be.

Therefore, people are heading for the lifeboats now, while the rules are the same. After January 31? Expect investment in London to collapse as it swings to New York. That will still be operating under the same rules as before, since the US never was part of the EU.