I've just got into Barcelona, and thanks to the Spanish penchant for late night dining, I've made in time for supper at the best tapas restaurant in Barcelona.
Cerveseria Catalana (Carrer de Mallorca 236, 08008, Barcelona), is blessedly close to the Esendex Espaņa office as well as a couple of reasonable hotels that you can generally get a deal on through booking.com
Menu highlights for me are the Solomillo de Tenera (small steaks skewered with a pepper onto a slice of toast) and Pimentos de Padron (roasted chilli peppers with salt, only the occasional one is hot)
On a popular night you'll have to queue but it is definately worth it. Keep an eye out for spaces at the bar. Same food but a bit more going on.