UK Stocks-Factors to watch on April 4

April 4 (Reuters) - Britain's FTSE 100 index is seen opening 8 points lower at 7,023 on Wednesday, according to financial bookmakers. * WPP: British advertising group WPP Plc said on Tuesday it was conducting an investigation in response to an allegation of personal misconduct against its chief executive, Martin Sorrell, who denied wrongdoing. * BRITAIN RETAIL: British shop prices dropped in March at the fastest pace in more than a year, adding to signs that inflation pressure c