I think I've solved your issue, or at least I had a very similar one which led me here earlier.
Simply put:
Change your boot mode from UEFI to "legacy support" or similar.
What I did:
Excuse the fuzzy instructions but my Windoze (10) is busy being Linux! Go to PC Settings > search "Recovery" > Advanced Reboot > in there you're looking for "Troubleshooting" then "EFI setup" - excuse a missing click if there is one.
More help for those in more of a pickle can be found here:
https://www.lifewire.com/how-to-access-advanced-startup-options-in-windows-10-or-8-2626229
Once you're in the actual EFI go Boot options and look for "boot mode", hopefully a quick change to legacy (BIOS) support helps your live CD. Remember to change this back asap when you're done!
While you're in EFI make a mental note of "secure boot"'s status as when you boot this disc in the wrong (command line/EFI) mode it does say you may need to disable secure boot if it doesn't work. Hopefully this should never be an issue with legacy mode though.
Bonus info: Some bootable discs support both EFI and BIOS booting properly, and may have different versions included for each (e.g. Memtest86). Make sure you know what's what so you load the most feature rich version - or have a backup method in case one doesn't play nice like this f****** Rescue CD in EFI mode ;)
Hope this solution is valid for someone