For anyone else trying to make this work - I've finally gotten my solution to work.
The code is based here:
https://github.com/MrSimonC/Toggle-Mac-Function-Keys
but for brevity, here is the contents of the apple script file:
-- Apple Script (i.e. Use in Apple's Script Editor Application) to Toggle Function Keys / Media keys on/off
-- Tested on MacOS Big Sur (11.4) June 2021
-- Project Path: https://github.com/MrSimonC/Toggle-Mac-Function-Keys
tell application "System Preferences"
set current pane to pane "com.apple.preference.keyboard"
end tell
tell application "System Events"
if UI elements enabled then
tell application process "System Preferences"
repeat until exists tab group 1 of window "Keyboard"
delay 0.5
end repeat
click radio button "Keyboard" of tab group 1 of window "Keyboard"
click checkbox "Use F1, F2, etc. keys as standard function keys" of tab group 1 of window "Keyboard"
end tell
tell application "System Preferences" to quit
else
-- GUI scripting not enabled. Display an alert
tell application "System Preferences"
activate
set current pane to pane "com.apple.preference.security"
display dialog "UI element scripting is not enabled. Please activate this app under Privacy -> Accessibility so it can access the settings it needs."
end tell
end if
end tell
Hope someone finds it useful!
Simon.