OK, so I now have both the Oracle 32 & 64 plugins working.
- I managed to install Oracle Express for Win32
- I installed Oracle 12 for Win64
Since Win64 does not do debugging, you need Oracle Expressed installed on a virtual machine as well.
The main trick I learned is that despite not being asked, you need to reboot after each step and resist the temptation to try and start something until after rebooting.