Does anyone know how i can access the function keys whilst using the surface pro 3 without the keyboard attached, i.e. how can i pull up the function keys from the surface keypad ?
There's an option to enable the Full Keyboard Layout in Windows 8 that should get you what you want: http://www.pocketables.com/2013/02/windows-8-tip-enable-the-full-virtual-keyboard.html
Under PC Settings, go to General, and then toggle the "Make standard keyboard layout available" to On.
Addendum to @music2myear's answer: after you enable the full keyboard, that just adds it as an option to the keyboard mode switching button that's on the (right?) side of the virtual keyboard. You then need to use that button to switch to the full-layout keyboard.
I have no idea why they make it so hard to discover that the full keyboard even exists. I rarely use anything else.