For those interested, I couldn't find any easy fix for this. So what I did was wipe my tvheadend setup.
After this, I re-added Matt's tvheadend IPTV channels via his guide. Then, I added the xlmtv https://www.xmltv.net/ EPG to tvheadend. This required adding a downloading script to my machine, then the EPG grabber module within tvheadend to grab the EPG from the xmltv script.
Then, after that I had to go into each channel within tvheadend and select the new EPG for each channel individually. (Config -> Channel / EPG -> Channels -> Edit - EPG Source - Select xx.yourtv.com.au)
This fixed the issue for me, the EPG is a little more detailed as well. If this helps anyone and you need more info, let me know and I can try to expand.