HELSINKI (Reuters) - Apple has sued Nokia in Britain, extending the two technology giants' legal battle over patents beyond U.S. borders. "We are investigating the claims, which appear to be based on nine implementation patents already in suit between the two companies in the United States," said a spokesman for Nokia. The two companies have been locked in a legal tussle since last October, when Nokia sued Apple and said the iPhone maker was using its patented technologies without paying for the