I am totally unqualified to start a Fideuà thread, but I'm not going to leave it to people who've eaten it in Catalonia to champion this dish
I was formally introduced to Fideuà/Fidegua by a Gandian friend whilst staying with his family in Gandia. It was delicious and something I will be hunting out in the future.
The Gandians acknowledge the following places as making good Fideuà:
El Rossinyol, Náquera (Valencia)
Casa Granero, Serra (Valencia)
this place looks fantastic for any of their rice dishes MAP
Hotel les Rotes, Dénia (Alicante)
El Langostino de Oro, Vinaròs/Vinaroz (Castellon)
And, completely out of Valencia:
Ginza Espero, Tokyo (Japan)
In Gandia itself:
Hotel Bayrén
Hotel Oasis Gandia Palace
Palau de Miramar