In reply to ranger*goy:
Mammut are definitely worth a look. I have a pair (size 38 - probably 10-12) that are longish on me - I'm 5 ft 8, and usually buy a 31" leg for casual use. As far as I know, those are the standard length, so if they also do a long, that would likely have loads to spare.
There's always Paramo for the ultimate in, era, practicality! They definitely do different leg lengths, and are very functional, but whilst they're great on a rescue, they don't look so good in the pub afterwards.....