I have a friend who works in Turkey (full time UN employment) and he got his visa extended last year (1st extension). Supporting documents could be a little different if you are self employed / company director etc.

Reading through other posts on board, it should be 3 yr extension for you.

1. Current vignette: Tier 1 General 2nd extension 2. Date of expiry of current leave: Feb 2014 3. Number of dependents applying at same time: 1 4. Date application posted: 23 Dec 2013 5. Date payment debited: 27 Dec 2013 6. Payment mode : Credit Card 7. Biometric letter received: 03 Jan 2014 8 ...