Ubuntu – Black screen on boot when any NVIDIA drivers installed

I have a machine with Ubuntu GNOME 15.10 and an NVIDIA GTX 970 graphics card. For the last few months it was working fine with NVIDIA driver 352.63 and CUDA 6.5 installed, however I recently tried installing CUDA 7.5 using the .deb from NVIDIA's site and running:

sudo dpkg -i cuda-repo-ubuntu1504-7-5-local_7.5-18_amd64.deb 
sudo apt-get update
sudo apt-get install cuda

After doing this, when my computer rebooted I was met with a black screen, with no mouse cursor. To fix this, I booted into recovery mode in grub and in a root terminal, typed:

sudo apt-get remove --purge nvidia*
sudo apt-get --purge autoremove

After doing that, I was able to boot back into a GUI (without NVIDIA drivers), however, whenever I try to install any version of the NVIDIA restricted driver or CUDA, I get the same black screen (even installing versions that worked previously) and I have to repeat the above commands to get my computer to boot again.

I have tried:

• Installing NVIDIA 352.63 using the 'Additional Drivers' menu
• Installing NVIDIA 352.93 using the 'Additional Drivers' menu

• Installing NVIDIA 364 using:

  sudo add-apt-repository ppa:graphics-drivers/ppa
  sudo apt-get update
  sudo apt-get install nvidia-364

• Resetting xorg.conf

• sudo dpkg-reconfigure xserver-xorg
• sudo apt-get install nvidia-common sudo apt-get install xserver-xorg-video-nouveau sudo apt-get install --reinstall libgl1-mesa-glx libgl1-mesa-dri xserver-xorg-core

• sudo apt-get install nvidia-modprobe nvidia-common

• Installing CUDA 7.5 using the .deb network file without first installing drivers

• Installing CUDA 7.5 using the .run file without first installing drivers
• Adding nomodeset to the grub config

Since installing the drivers that previously worked no longer works, I suspect that there is something I am forgetting to reconfigure/reset prior to installing.

Any help would be very much appreciated.