The only person of any consequence/power in UK is the raghead mayor of Londistan.
With London in hand, the caliphate is assured within 5-years. It could possibly include the remains of France & Germany.
When WWIII is fully underway (having already started), we will be facing the world Hitler envisioned if he had been victorious.
Even if you believe that the Mayor of London has such an ambition, your understanding of the power of the office he holds is grossly exaggerated. Directly elected mayors are a recent innovation in the UK. Although in some ways they were modelled on US city mayors, their powers are much more limited. Here is a summary of those powers for anybody who may be interested:
What can the Mayor of London Actually do?