NOTE: Silent Hill 3 has different costume codes, depending on the region; these codes are for region PAL, which includes the United Kingdom and Europe)

Finish the game to access the secret costume passcode screen. Enter the passcodes to unlock a new costume for Heather:

HappyBirthday (Heather Shirt)
I_Love_You (Onsen)
PutHere2FeelJoy (Block Head)
TOUCH_MY_HEART (Don't Touch)
GangsterGirl (God Of Thunder)
LightToFuture (The Light)
ShogyouMujou (Transience)
BlueRobbieWin (Killer Rabbit)
01_03_08_11_12 (Royal Flush)
cockadooodledoo (Golden Rooster)
PrincessHeart (Transform)
Shut_your_mouth (Zipper)