Rose’s girlfriend Tara Knaggs, 25, who had been on the phone to him throughout the pursuit, was jailed for three years after being found guilty of assisting an offender.
A fourth defendant, 25-year-old Samuel Aspden, another of Rose’s friends who had driven around the area in his own car the same evening, was cleared of both murder charges.
Mr Birchard died at the scene from head injuries, fractures to his face and skull and a severe brain injury, the court heard.
His father said in a statement: “William was not just a victim of a senseless crime, he was our beloved son, a brother and a friend to many.
“His life was filled with promise, and his loss has left a gap that will never be filled.”
Mr George died in hospital shortly after the incident.