UK Ad Firm Clinches Bid for U.S. Rival  LONDON/NEW YORK (Reuters) - British advertising company WPP  &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=WPP.L target=/stocks/quickinfo/fullquote"&gt;WPP.L&lt;/A&gt; said on Sunday it has won an auction for U.S. rival  Grey Global &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=GREY.O target=/stocks/quickinfo/fullquote"&gt;GREY.O&lt;/A&gt;, with what sources familiar with the  matter said was a cash-and-stock deal worth about \$1.34  billion.