I have Ubuntu 16.04.3 installation that had been running successfully with 17.10 drivers. Decided to upgrade to 17.30-465504 and ran into no graphical UI on reboot. Uninstalled/reinstalled; yes, I followed the instructions. Observed that the uninstall script that was promised was not there; had to run the installation script (which first uninstalls) in order to get earlier versions out.
Finally solved the installation problem with the assistance of Mark Maurer's post in "ask Ubuntu". Apparently despite keeping my 16.04 installation up to date, I needed to manually install the "Hardware Enablement Stack (HWE)". Once I did this and rebooted, I was able to follow the amdgpu-pro-17.30-465504 installation instructions successfully and get the new drivers installed. Rebooted and was able to log on through GUI.
Hope this helps...
Glad to hear you got things sorted.