They were always ahead after building a 4-1 first period lead. Scorers were Matt Hanna (4), Lee Cadwallader (2), Sam Adamson, Paul Williams, Alex Saunders and James Morris.
Grantham completed their matches with a 6-5 victory over South Derbyshire.
Bridgefield join Cheltenham Spartans, Cambridge, Castleford and Ealing in Championship 3.