I'm not 100% sure if you need to remove lower section of dash board, if you do remove o/s end trim of dash there should be 3x 25 torx bolts remove them and the underside of the dash section there are two more, remove them and that's your dash trim removed. Remove brake light switch by twisting to the left and disconnect connection plug. Fit sensor in the grooves and turn to the right until it clicks into position reconnect connection plug and test your brake lights they should now be working and then refit the dash section job done the epc light should go out but until you erase fault memory you will have a brake light switch fault sporadic logged