The Spanish edition of Ha'Penny is published today, under the title of The Conspiracy of Coltham (La Conspiracion de Coltham). Their version of Farthing was called The Farthing Set (El Circulo do Farthing) and no doubt they'll think of something similar to call Half a Crown. I'll find out when it comes out.
Nobody asked me, but I actually do have an alternate title for Ha'Penny, which I'd have used if I hadn't been using series titles. It's a thriller title, a Robert Ludlum-style title: The Hamlet Bomb.
I quite like the cover which is a nice classy thriller cover. Cory's quote about Guernica looks odd in Spanish, or rather differently weighted.
I know I have two Spanish-speaking readers, so I will probably find out one day if it's a good translation, but for now all I can say is it's out there.