Launch control

Extract from the 2014 Leon Manual, seems to imply that its on all diesel cars over 125 and all petrol over 140 with 6 speed DSG box.

You also have to disengage ASR have you tried that.

Launch Control Programme
3 Valid for vehicles: with Launch-Control/6-Speed
DSG with diesel engines superior to 125 kW and
petrol engines superior to 140 kW.
The Launch control programme enables maximum
acceleration.
Important: the engine must have reached operating
temperature and the steering wheel
must not be turned.
The engine speed for launch-control is different
on petrol and diesel engines. To use the
launch-control you must disconnect the antislip
regulation (ASR) through the Easy Connect
system menu ››› page 81. The warning
lamp  will stay switched on or will flash
slowly depending on whether or not the vehicle
has a driver information system*.
On vehicles with the driver information system,
the ESC lamp lights up permanently and
the corresponding text message Stability control
deactivated (temporary) appears on the
instrument panel to indicate the deactivation
status.
– When the engine is running, switch off the
traction control (ASR)1).
– Turn the selector lever to the position “S”
or tiptronic, or else select the sport driving
mode from the SEAT Drive Profile*
››› page 169.
– Press the brake pedal firmly with your left
foot and hold it down for at least one second.
– With your right foot, press the accelerator
down to the full throttle or kick-down position.
The engine speed will stabilise at
about 3,200 rpm (petrol engine) or about