Thanks for input everyone. The Natures Head separates the pee out so I shouldn't get it too soggy no matter how many people are using it. My worry was more that it would get too dry just using the Aubiose (Hemp horse bedding in 25kg bale). A mix of compost and hemp apparently is the way to go!
I got pond gloves from my son for Xmas for use down the weed hatch. I suppose they could double up elsewhere, provided I was careful walking through the galley on the way from one to the other!
I am pleased to announce that my loo is now connected to the 12v system as well as to the solar vent so venting should be wonderful. Again reading other comments the loo is miles away from the steering position.
I almost can't wait to use it...