Konami has clarified that both titles are available for PlayStation Portable only, and are not compatible with PlayStation Vita.
Konami has released Silent Hill: Origins and Silent Hill: Shattered Origins, two quality (though somewhat divisive) series entries, on the EU PlayStation Store for £7.99 apiece.
Origins acts a prequel to the series, while Shattered Memories is a re-imagining, not a remake, of the original, PS1 Silent Hill. If you're looking for maximum thrills, they'll probably come via Shattered Memories--there are no combat elements, which means you'll have to run from every nightmarish opponent in the city.
The Silent Hill series hasn't been a critical darling of late, with 2012's Book of Memories on PS Vita scoring a 6.5 and the same year's Downpour scoring a 7.5. Still, good things could be coming--we've heard rumors of Silent Hill: Otherworld dropping in 2015, but the evidence has been shaky.