Correspondence with TheGreek has motivated me into updating this thread a little bit. Not much to report, I've managed to source most of the parts, but still after a neck. I'm aware there's a few out there but, as before, don't have much money to spend on this as yet.
Here's the things I now have;
P and J pups from a old Yamaha RBX
Wiring loom and pickup selector switch courtesy of KiOgon
Bridge assembly from a Hohner B2A
Knobs from a Yamaha RBX
Strap pins from my spare parts drawer
Well seasoned Cherry body blank
I'll be copying the shape of the RBX control cavity so as to utilise the cavity cover that came with it!
Steinbergers et al. come with a strap button extension arm so as to make wearing the instrument more comfortable. I'm thinking of ways I can make one. The best idea I have so far is to get some metal tubing, plug one end with a dowel and screw the button into it. I can then either affix the extension into the body by drilling a hole in the side of the body for it to sit in, or by shaping a channel in the back for it to lay in which I can then secure in place using bolts or something.
Progress is slow, haven't even shaped the body or anything yet! I can't really do much until I have a neck. As Kiwi pointed out, I need to know how the neck and bridge work together before I can design the body and build it!
Cheers
Alex