This will not happen. If the government (or Ofcom if the bill goes through) is seen by the populace to be the cause of WhatsApp being withdrawn from British us

This will not happen. If the government (or Ofcom if the bill goes through) is seen by the populace to be the cause of WhatsApp being withdrawn from British users the outrage will be deafening. No administration would do such a thing, even the incompetents in office at the moment. (quite possible is a terrible PR own goal followed by a u-turn, however)