Yeap like Ian (IJ) i've also been there done that and didn't get the T-shirt either (bastards ripped us off). I just soaked the shit out of it with PB blaster and the right before taking it out with a big easy out, I heated the left over portion of the banjo fitting that is still in the head. Came out like a breeze. Focusing the heat on the on the fitting also help loosen the rust that is seizing it in the head.
You'll most likely have to pull the head at a minimum cuz there is not enough clearance to get in there to work on it. Also another thing that helps is if ther is enough still protruding out past the head, use a punch and hit is a couple of time on the side around it as much as possible and also a couple of light blows straight down on the fitting will help releave any binding of the threads.
A little insite is that when you put a new one in, use some Anti-Seize on the threads and I take it out once a year and put new seal washers and more Anti-seize on it. It comes out every time like a breeze. I figure, mine was sopost to be a $20 some odd dollar job and about 20min's. and turned into a $500 dollar job that put the car down for a weekend (decided to rebuild the head while I had it off and install a MLS) so I figure a little preventitive maintance will keep that from happening again.