Sept 19 (Reuters) - Rolls-Royce Holdings Plc is looking to raise around 2.5 billion pounds ($3.2 billion) from investors and is in talks with sovereign wealth funds, including Singapore"s GIC, the Financial Times reported here on Saturday. The British aero-engine group is planning to launch the equity raise in the first weeks of October, the report said. Rolls-Royce and GIC did not immediately respond to Reuters requests for comment.