Law 14 - The Penalty KickHi Guido, not taking sides here, but found this (don't know if it's still valid)
https://www.fifa.com/mm/document/afdeveloping/refereeing/law_14_the_penalty_kick_en_47369.pdf
On page 7 it says
"Feinting to take a penalty kick to confuse opponents is permitted as part of football.
However, if in the opinion of the referee, the feinting is considered an act of unsporting behavior the player shall be cautioned."
Cheers mate. On the FA's page it's more detailed and expressly makes reference the act of a feint in the run-up is acceptable: "feinting to kick the ball once the kicker has completed the run-up (feinting in the run-up is permitted)".