My finger slipped when logging into facebook and now all my contacts from facebook have synced onto my phone and I can't find any bloody way of undoing it !! I can't even delete contacts one by one, there's no option !
I don't want this, I had everything organised on the phone now its all gone tits up.
Anyone know how I can rectify it ?

Go to settings in the Facebook app and there should be the option to remove the synced data. I did the same and it worked.

You could also try logging off from facebook and logging in again. (well it seems to work this way on my daughters Galaxy Ace)