Heat the wine and onion in a saucepan over high heat. Add the mussels, cover and gently shake the pan for 5-8 minutes. Remove from the heat, discard any closed mussels and drain, reserving the liquid.
Heat the oil in a large heavy-based frying pan, add the extra onion, ham, garlic and red pepper, and cook for about 5 minutes. Add the chopped tomato, chorizo and cayenne pepper. Season. Stir in the reserved liquid, then add rice and stir again.
Blend the saffron with the hot stock, then stir into the rice mixture. Bring to a boil, then reduce the heat to low and simmer, uncovered, for 15 minutes without stirring.
Put peas, shrimp, squid and fish on top of the rice. Push them in, cover and cook over low heat for 10 minutes, turning over halfway through, until the rice is tender and the seafood is cooked through. Add mussels for the last 5 minutes to heat through. If the rice is not quite cooked, add a little extra stock and cook for a few minutes. Leave to rest for 5 minutes, then add the parsley and serve.