LONDON -- Google is developing a new U.K. headquarters which could be worth as much as $1.6 billion when finished, the latest overseas property deal for the cash-rich U.S. Internet group. Google (GOOG) has purchased 2.4 acres at the Kings Cross Central development, one of London's biggest regeneration schemes, where it will build a 1-million-square-foot office, property developers behind the project said on Thursday without disclosing the purchase