When changing my PS3 HD to AV scart i chose the wrong option (PAL) is there anyway of changing it back??

May be...

yes you can default it.

for example if you turn on your ps3 and the screens black (nothing starts up) the way to fix this is by when ps3 on where the green light is (start button) touch and hold this button for about 10sec until it restarts itself and the settings will default. if this doesnt work email me at horizontal_kevin@yahoo.com

ill help you through this 8D

I got a free Playstation 3 from this site, I highly recommend it!