This is one of my friend's timeline am posting here so this one is not mines as mines has been approved and ceremony booked already.
Eligibility criteria: ILR 3 years (Received from Spouse)
Application type: Posted Himself
Date of application: 23/10/13
Date of receipt by UKBA: 24/10/13
Date of debit of fees: 13/12/13
Date of acknowledgement letter: 14/12/13 (dated 13/12/13)
Date of approval: 15/01/14 (dated 9/1/14)
Date of Ceremony:26th March
So this is my friend timeline, we submitted our application at the same time and now we have both been booked to attend the ceremony on the same date.
I also decided to post his timeline because I wanted all those people who applied within our batch and that's from October 21st- October 25th 2013, that it looks as though things are really moving in the HO now. My advice is that based on average, it's taking the HO one month from the date they debited your account to approve your application. So all those in this batch who had their fees debited in December your approvals will probably be on its way as January has not finished yet. If you were debited in January then at least give it till February but lets hope it comes before then.
So I just thought I would help to ease and relax some nervous minds, am sure your brown letter is on its way just don't fret am sure it will drop through your door when you least expect it.