The Sussex side were made to fight all the way in a repeat of last year's final to secure their final berth against Surbiton, who earlier had beaten Loughborough Students.
Internationals Mark Pearn, with a hat-trick, and Ashley Jackson led the Grinstead goal scoring machine with five goals between them, but the goal of the match went to Dave De Prez.
The leading goalscorer in the National Indoor League premier division this season, he was on target again with a superb revere stick flick. Captain Scott Ashdown completed the rout.
Cheered on by a bunch of loyal travelling supporters at theTrent FM Arena in Nottingham, Grinstead will defend their championship title at 5.30pm this afternoon determined to prove they are the domestic leaders in indoor hockey.
Next month they will be flying the flag for England at the European Indoor Club Championships in Vienna.