Zuckerberg is hardly going to turn up to answer questions from a group of British twopenny-halfpenny politicians is he. Facebook is global and your laws start and end at Dover i.e. zero jurisdiction over the web.
I suspect Russia and North Korea will be taking a great deal of interest in the TSB infrastructure and other UK banks that have outsourced their IT/Ownership/Responsibility/Security (tick all that apply) based on this evidence.