I believe we all have heard Andrew Jennings allegations regarding all this in the past.
LIke they say "When you hear the river flow, its because it carries water"
Corruption in FIFA is well known, in some countries the President of the association hold that post until his death. Some of them have been there for more than 20 years. In the end its a lot about money.
As for the bids, well, I reckon, that England has the best structure to secure the bid. Great fans, great stadiums, great infrastructure, etc.
In Spain, they say it would be really unfair if England gets it. They still live in a state of euforia after their WC win and believe they should attract all attention.
As per the two other bids, I believe FIFA is not so fond of a two-nation bid. I actually would love it to be either in England or Russia. I mean Russia never hosted a football tournament. They got the money, and probably will mean a huge economic boost to the country.
Oh, one more thing... If England doesnt get this one, they will have to wait 20+ years more, because of Continental rotation enforced by FIFA