So here we have the assembled bottom bracket fixture (the bottom bracket shell is the dark tube bit sandwiched between the knurled nut and aluminium bottom locator).
The studding is just cheapo 12mm stuff from B&Q (£3.50ish for a meter).
And here we have the exploded assembly to show you the internal detail. Hopefully if I start making a few frames I can get all of this re-manufactured in precipitation hardened steel to make it a bit more hardwaring.
Next up will be the seat-tube locating nut and mounting plate......