In the picture above you can see the Radio Times dalek I started a few years ago and on the right the new one built to the guild plans.
The base is 3/4" plywood and the other horizontal parts are 1/2". The panels are cut to fit and are 3/8" thick plywood.
I decided to use hemispheres pushed through holes in bathroom panel for my skirt. I think this probably wasn't very wise, as it's made respraying very difficult. The hemis were bought as complete spheres and laboriously cut in half with a junior hacksaw. I attached these onto the skirt using Duct Tape(!). There seems to be no end to the uses for that stuff.
Some people use plastic xmas decorative balls, some people fibreglass their own from a mold, some people push mold them from vivak, some people buy sets of them from other fan builders.