THEY are getting worried in the banking world about the advent of the euro which will deprive our hard-pressed financial institutions of all the lovely loot from currency transactions. Apparently one cunning entrepreneur has patented the word "euro" and is looking for royalties from the EU for its use. "At last, someone has figured out a way of making money out of the single currency," was the wistful comment of one institution's newsletter. The bankers privately hope that the single currency will go the same way as the Ariane rocket. And would happily push the self-destruct button.