METALS-London copper edges down; China congress in focus

(Adds comment, detail, updates prices) By Melanie Burton MELBOURNE, Oct 18 (Reuters) - London copper on Wednesday eased from three-year highs hit earlier in the week, but was supported by solid demand-growth expectations, with markets looking to policy announcements from China's Communist Party Congress. "China's underlying demand for copper remains stable and solid," said Hong Kong-based broker Argonaut Securities. There has been stable demand from China's power sector, and st