One word of caution (being a lawyer!) - its not as straightforward as it seems! I get the impression (I may well be wrong!) these cases have been successful because the banks have not bothered to reply to the claim and the Claimants have obtained 'Judgment in Default' - i.e they've won their case because the banks haven't been a*sed to reply.
When u sign a written document (i.e account application forms aka 'small print') u are bound by its terms even if you haven't read any of it. Therefore the banks will soon start winning their cases once they've got wind of what people are up to.
Having said that, if you're planning to sue - good luck!
Then again, u could always store your money underneath your matress instead!