What sort of race is it? Are you sure you really need waterproof gloves - or do you just need to keep your hands warm? The reason I ask is that once full of water, all waterproof gloves do is hold it in!
Based on very little knowlege of what you intend to do, I would suggest looking into neoprene gloves (as sold to fishermen) as a possible contender.
It's the Lakeland 50 miler so with it being up there it's bound to rain and I need to be navigating. Did an 18 miler in Brecon the other week and my hands were soaking and cold and thought I could have a problem over 50 miles if the weather turns bad. The gloves I run in normally in the winter will be useless if it pisses down all day!!
I have another idea along the lines of neoprene gloves. Have a look at sailing gear retailers. They often have gloves witha neoprene back and leather palm. Not waterproof but warm when wet without sacrificing all ability to use your hands.