I've had problem with Munton's Maris Otter before, including haze. Did you get the expected extract with it? When I had the haze problems, I also had lower than expected extract. It happened on more than one bag, so I just concluded that they make crappy malt and spent more time getting better ones. But I haven't heard people complain about Fawcett in the same way, so I'm assuming you got a bad bag.
I basically got rid of it by making dark beers and ignoring the haze problem. I sometimes would get a lesser amount of haze from some continental Pils malts, so I normally throw in a short (10 min or so) rest at 131F/55C. Not sure if this would help with this problem, but you might give it a shot.