I think Left Handed it would have to be Elizabeth Horne (nee Talbot) as she's never been beaten in Britain with her left, and has beat the likes of Sue Owen, Elaine Pickup and many others. Right handed it's a different kettle of fish, and those names are right on the mark.
Elizabeth's only defeats ever left handed have been by two russians, the great Vika Gabagkova and Zarina Bzarova in Poland at the World's in 2001 when she got bronze. Elizabeth was only 17 then, and is a LOT stronger now.
Anyway Eliizabeth is looking forward to next year with the World's in Italy as her goal, along with the World's Strongest Woman comp again.