Who said anything about blasting their way into London? It could be done quietly and probably with the Brits' help. I'd bet they'd love to get rid of that subhuman piece of pigshit, too.
He is being held by the British Police, on the order of the British Government in London. What are a special ops team going to do? Are you seriously suggesting a covert operation to kill a prisoner of the US's strongest ally, on that ally's territory, in contradiction of that ally's law?
I can assure you The Brits would be up in arms. There is a time and place for diplomacy. Life is not a movie