Hmm, might be worth asking the organisers about that one!
You could look at some shell type mitts to go over your thermals; might be more acceptable to Fellsman kit checkers.
I'm doing PPP this year so will miss out on all the fun. 2012 was a blast for my first fellsman and I'll be back again. Trying not to leave it too long; the way things are going we'll need an army bergen for all the mandatory kit before long!