I'm not entirely sure about leaving them all to die.
While nearly everyone in the table (sans Penwood) are essentially worthless, I'm more concerned about the comms officers.
If they can last longer, they can rally and coordinate the resisting mundane british forces. Those in turn would not deal any significant losses against Nazi vampires, but they could delay them enough for more civillians to evacuate London.
The question is how much Tomi can help (bec. leaving Yanagawa and Miyako is out of the question). Also, as long as she doesn't encounter any hero units, Tomi could also slip away once the situation is too far gone.