Can you just pull the pipe away from the wall a bit and gut a mini pupe cutter around it? If not, you should be able to pull it off the wall just anough to wedge something behind it and use a hack saw on it. Though, a guess a grinder would work as well. Make sure you debur the cut end well. You can just slide a piece of sheet metal or other noncombustible material behind the pipe and solder away. Keep a fire extinguisher around just in case. I have never used the presoldered fittings, but I have heard that they are fine. I do not think they offer much of a convenience though. Good luck.