I am sure there are many others that are able to build, but I only know Ben. I think he's done most of the building of Disto's for CHECC, ULSA (for [somewhere in?] Yorkshire resurveying project) and quite a few Derbyshire and Yorkshire cavers.
I included a bit of waffle about Duncan meeting him in the hunters last Thursday. and that I rent a room in Ben's house.
Ben can be contacted on here (Benfool), but I didn't want to advertise for him, cos his mother was a hamster and his father smells of Elderberrys.
If there's any other people who can also make them, it would be good to mention them as well, for balance, I guess.