I often find it hard to find allies in declaring war against other Civ, once I had a game as Carthage, and I have the Celts, Byzantines, and China as my ally; we all commonly hate England who is allied with almost all of the city-states in the game... By the time I was prepared for an all out invasion against England, none of my allies would want to attack England despite all their hatred against it, I have lots of gold and resources but yet they don't want it at all.
I think you are doing it wrong! Did you see if you could bribe England to attack the Celts, Byzantine, and China? It feels wrong, but that's how you get your friends to help! Of course, you DoW England the turn after she accepts your bribe...
If you really have lots of gold, bribe your way to allied status with as many CS as possible right before your DoW on England.