David Beckham's string of lucrative sponsorship deals seem safe for the moment despite allegations that he had a fling with a personal assisstant.Mobile phone giant Vodafone said, 'It is a private matter for David Beckham to deal with.'Soft drink giant Pepsi refused to be drawn into the controversy.Beckham signed an extension to his multi million pound sponsorship deal with German sportswear manufacturer Adidas last month.A company spokesman dismissed any talk the allegations would impact their relationship with the Real Madrid star as 'silly.'High Street chain Marks and Spencer, which has worked with Beckham or a range of childrens wear, were...