Unilever PLC (LSE:ULVR), Nestlé India Limited (BSE:500790) and Coca-Cola India Private Limited have begun due diligence on GlaxoSmithKline Consumer Healthcare Limited (BSE:500676) which includes Horlicks and Boost, and is estimated to be worth about $4 billion, three people aware of the developments said. Spokespersons at HUL, Nestle and Coca-Cola said they wouldnot comment on ‘speculation'.