The last internal from BAA has this timetable.

Date: 25 February 2009
Iberia (with Clickair) will move from Terminal 2 to Terminal 3

Date: 16 June 2009
Lufthansa, Swiss*, Austrian, Croatia Airlines and TAP Portugal will move from
Terminal 2 to Terminal 1

Date: 26 October 2009
British Airways and Qantas move from Terminal 4 to Terminal 3
Jet Airways, Gulf Air and Malaysia Airlines' move from Terminal 3 to Terminal 4

Date: 27 October 2009
Air France, Alitalia, Korean Air, Aeroflot and CSA Czech Airlines' move from Terminal 2 and Terminal 3 to Terminal 4

22 non-aligned airline moves from Terminal 2 to Terminal 4. Please note, these moves will be phased in from 27 October 2009 to November 2009. Actual move dates are currently being agreed with the impacted airlines.

Date: 9 February 2010
Biman Bangladesh Airlines, Royal Brunei Airlines, Kuwait Airways, Air Mauritius, Qatar Airways & Saudi Arabian Airlines' move from Terminal 3 to Terminal 4

Date: 30 August 2010
Air India and Etihad Airways' move from Terminal 3 to Terminal 4