Thanks Etienne, but this doesn't seem to have worked!
Here's what I tried:
1. Flash device
2. When FTU screen comes up do -> adb shell stop b2g
3. push user.js file containing that pref (contains some other prefs
too which work so I know it is valid)
4. adb reboot
5. Connect to Wifi, wait.. it will check for updates :(
Note that these are updates for the HERE maps and other apps installed
rather than OTA updates for Gaia itself. Are they separate or part of
the same update process? I want to stop both.
Cheers,
Zac