You don't need to go on the PC store. They all show as Free on PS+ from the Vita store whether or not you've already grabbed the other versions of the games :)
Great month to fans of real games. Saved me a bit too as although I already had Steamworld Dig (Fantastic 3DS game!) Luftrausers, Binding of Isaac and Escape Plan were 3 games I was unsure of, and Hungry Horde I'd never even heard of until last week.