"Unfortunately for you fn keys are not passed to the OS and are all translated in the hardware (/ firmware) before the OS sees it.
Your best bet that you may not like is just to use a external keyboard. I use one and would not go back to using the laptop keyboard if I did not have to!"
The best remapping tool I've found is SharpKeys. It won't handle the fn keys for you, but it will allow you to map end and home to something else on the keyboard.
