Remover claims that removal of Sophos AV successful, alternate antivirus claims that incompatible software found (Sophos Antivirus) and requests removal of that software prior.

I installed what I believe to be Sophos Antivirus (home version) some time in the past few months. Later I decided to change to an antivirus that better suited my needs. 

At first I forgot to remove sophos, and ran the installer for the alternate software. It ran a compatibility check, and as expected found Sophos AV to be incompatible software, requesting that I uninstall it first before attempting to install my desired software.

Using the uninstaller/remover bundled with the Home version of Sophos Antivirus, I removed the AV, and the remover said it was successful.

I then attempted to install the antivirus I found better suited to my needs. Again the installer ran a compatibility check, but again it found incompatible software and asked me to uninstall sophos antivirus.

I restarted the computer and tried again to no avail. I also downloaded the removal tool again, separate to the bundle that came with the installer, and ran it, again it said the removal was successful, but again my desired software said that I needed to uninstall sophos. 

How can I completely remove sophos antivirus from my laptop? I currently have no visible sophos software on my laptop, and thus can not check the version I was once running.