The Plymouth side actually took the lead on five separate occasions and were 11-9 up with five minutes remaining. But goals by Lauren Keight and Claire O'Sullivan brought Birmingham level with 31 seconds remaining. Then Lauren struck with her last-ditch winner.
Southampton's girls beat Polytechnic 10-3, including four goals for Tansyn Scortino and three by Michelle Foules. In men's Division Five, Castleford retained top spot by defeating Dover 17-6 while four goals apiece for Freddie Person and Edward Govier ensured Invicta Marlins' 12-6 success against Sheffield Dolphins.