It turns out this bodged in resistor near one of the legs of the HDD bracket was shorting against it. I added some kapton tape to it and the machine turned on! 
Unfortunately the HDD is now not fully spinning up. It tries for maybe a second before giving up. Tried a bunch of cycles but it hasn't kicked on yet. Hoping I can get it working so I can image it. But worst case I can replace with a ZuluIDE and use one of the images @zigzagjoe posted on MLA.
Unfortunately the HDD is now not fully spinning up. It tries for maybe a second before giving up. Tried a bunch of cycles but it hasn't kicked on yet. Hoping I can get it working so I can image it. But worst case I can replace with a ZuluIDE and use one of the images @zigzagjoe posted on MLA.