In my mind, it would be HEHR-uh-ward/wərd because the pronunciation of Hereford (which is a town in England but similar to Hereward in terms of how they look) is HEHR-uh-fərd.
When I looked at the pronunciation on this website (
http://www.pronouncenames.com/pronounce/Hereward), the first and last entries put it as "HEH- ruh- wuud" and "HErruh-'wood' // 'HAIR'-uh-'wood'" respectively and that fits closely to what the pronunciation is in my mind.
~I luv London Tipton 'cause she's an idiot like moi~
My pinool:
http://www.behindthename.com/pnl/149249