The sides were level at 6-6 after two periods, but South Derby dominated the third, building a 12-8 lead with goals by Neil Swainson (3), John Houghton, Conor Brady and Craig Mellors.
Bedford and Sheffield Dolphins reached the end of the third period at 7-7 before Bedford clinched the points with a 9-8 win. Goals by Charles Costin and Justin Irvine made the difference, Sheffield's only response coming from a man-up goal 33 seconds from the end by James Newsam.
Portobello were too strong for Grantham, winning 16-7, including seven goals in a dominant third period.