Seat LEON SI stops occassionally and EPC light comes on. ?

Check the brake switch is correctly set and the brakelight bulbs are working properly as they will affect the EPC.
If they are ok then, with the engine off, press the accelerator to the floor a few times (20 or 30).
This might help to clean the EPC sensor for a little while, but I wouldn't be too hopeful.
You may well have to replace it.
EPC = Electronic Pedal Control

asf
May 2009