1) Three – Harriet Jones, Harold Saxon/the Master, Jo Patterson. ‘Jeremy’ in The Green Death is seen from behind but we don’t hear him speak (and he’s arguably not fictional, if he’s supposed to be Liberal leader Jeremy Thorpe).
2) Three – we’re including the Master even though he was resurrected later, and as well as Patterson there’s the unnamed PM who’s killed in Aliens of London. 3) Winston Churchill.