iirc money mostly enters Britain because they use it as the way point for the tax havens "controlled" by Britain; their overseas territories and crown dependencies. Then it disappears into the land of political and financial voodoo of nameless holding companies, trusts and such, where nobody knows who is responsible for what, in both holdings and regulations. Mossack Fonseca's Panama Papers were a fairly big deal, but in reality that was the tiniest glimpse into that opaque world, and the revelation ended up changing nothing. Politicians still campaign about tax rates as if they mean anything when they can just be avoided.