The Overground timetable from December 2012 is now online.

http://www.tfl.gov.uk/gettingaround/6391.aspx

The good news is the Clapham Junction extension will be operating. The bad news is we'll have fewer trains going to Highbury & Islington. The Crystal Palace service will still terminate at H&I but the West Croydon service will terminate at Dalston Junction. This is to free up space at H&I for the Clapham Junction service.

Thanks for the heads up on this
Thankfully my train is still the same time, phew

The loss of the direct H&I services from West Croydon I can live with, just change at Dalston Junction and the train behind will continue. Same for H&I on the way back, the new Clapham Junction train allows interchange with the West Croydon train from Dalston.

Southern are also retiming Sunday services from London Bridge on our line from December.