UK law is very broad in its protection of consumers against "products" that are presented in a deceptive manner.
You mean like just about every software license agreement in the world? ;)
If people get really rowdy, refund anyways. Shoot even if it's late refund. I'd be super lenient with it, you will make plenty of money.
About the only criminal area you need to worry about is mail fraud. Which would be fraud while using the U.S. postal service. But that's not a real concern either, as your only using mail to process refunds, not to solicit. You also don't need to use the mail, as you can require faxing or email of birth info. btw, IANAL.
I think if you offered a no questions asked moneyback guarantee for wrong predictions, then the only people paying would be people whose predictions were correct (assuming every person with a wrong prediction requested a refund). You would of course put a disclaimer (as psychic hotlines do) that it is for entertainment purposes only, etc.
There's a reason for that little line.