A simple switch has three connections often marked Com - L1 & L2.
Your arrangement has two simple switches mounted on the same base so you'll have six connections in total.
Power typically connects to Com and goes out on Either L1 or L2 depending on the whim of the person who wired it up.
When I don't like the way a switch operates I sometimes swap over L1 for L2 (or vice-versa) and sometimes I leave the connections as they are and just turn the switch plate the other way up.
To achieve what you want just swap over one of the L1/L2 wires.
Peccavi
February 2009