Not sure when they will revert - I have a similar time line - complaint in feb 2017, in mediation till October 3017 when it moves into investigations. You should ask them have they issued a letter to finance institution looking for their position (mine issued end Jan and the bank have till end feb to respond) so I will be following up with FSO in March re timelines. Your complaint could be on a similar time line so I would call them and check. FYI, when my complaint went from mediation to investigations the mediator warned me that investigations are working on a 12-18 months time frame!!