BBC reports HMS Echo joining search http://www.bbc.co.uk/news/world-asia-26659583 (it's in the colomn to the left of the pistures - which aren't live at the moment)

Echo is a survey vessel, more info about her here http://www.royalnavy.mod.uk/The-Flee...Ships/HMS-Echo

Not clear where she actually is at the moment but at the top of the page it tells you where she was on the 18th - which isn't the southern part of the Indian Ocean