At 06:53, before daylight, DHC-8-402Q G-ECOO requested and received permission from ATC to push back and start from Stand 9, to face north and to hold south of Bravo One Taxiway (approximately abeam Stand 7). This was a non-standard pushback to allow a Jetstream 41 on Stand 11 to taxi out via Bravo One, to Runway 02. This was completed without incident, the tug was then disconnected and all personnel and equipment cleared from the area. One minute later the Jetstream 41, having already started its engines on stand, requested and received permission to power back from Stand 111. At the end of the manoeuvre it stopped on Taxiway Alpha abeam Stand 10 and Stand 11. When DHC-8-402Q G-JEDO requested permission to push back and start from Stand 6; ATC instructed it to ?STANDBY?. The Jetstream 41 was then given permission to taxi via Holding Point Bravo One, back track, line up and takeoff from Runway 02. G-JEDO was given permission for a standard pushback and start from Stand 62. In attendance were a headset operative and a wingman positioned to the south of the aircraft, and the tug driver. Prior to commencing the pushback the headset operative indicated the direction of the pushback to the tug driver using hand signals. Two minutes later, having seen that the tug was disconnected from G-ECOO, ATC asked the pilots if they were ready to taxi; they replied they would be in about 30 seconds. ATC replied, ?TAXI PLEASE WHEN READY [HOLDING POINT] BRAVO ONE?. The wingman had by then left Stand 6 for another task. As G-JEDO?s pushback neared completion it slowed and then stopped on a heading of approximately 220§. The headset operative asked the commander to confirm that the aircraft?s brakes were OFF, which they were, then reported that they could not push the aircraft any further and asked for the aircraft?s brakes to be set ON. A passing Airside Operations vehicle reported to ATC that there was an ?AIRCRAFT TO AIRCRAFT CONFLICT ON STAND 6.? G-ECOO then transmitted to ATC ?WE JUST FELT A BUMP? and asked for confirmation that they had been hit. After photographic evidence had been acquired, both aircraft were pulled back onto stand. G-JEDO sustained damage to its right elevator, G-ECOO sustained damage to its tail cone