BUZZ-Publicis: best day in 16 months on surprise Q1 growth
** Publicis (Paris: FR0000130577 - news) rises 5 pct after posting 0.8 pct Q1 organic growth v contraction expected by analysts
** Traders also cite Q1 organic sales of 2.1 bln euros as being slightly ahead of consensus
** Best day for stock since December 2013, among most traded by average volumes on Stoxx 600
** Peers also higher: Havas (Other OTC: HAVSF - news) rises 4.5 pct, WPP up 2 pct
(RM (LSE: RM.L - news) : alasdair.pal.thomsonreuters.com@reuters.net)