Two batches ago I brewed a bitter with Muntons that had a 11/16 date. It worked fine.
I love Munton's ale yeast because it's so damn cheap. I think my last pack was... wait, I can even look it up..... heh.... $1.13, including tax! And made a great stout that won a gold. I should use it way more often. The "drawback" is the terrible attenuation, I got just 56%. But hey, if the beer tastes good, who cares. Could always increase the OG and/or do an overnight mash (low & slow = the way to go) to help compensate for the low attenuation.