Though discworld works and I suppose is playable does anyone know how to bring up the ingame context menu (F1) using a joypad. Without this menu you can't exit the game as this game doesn't seem to allow the default scumm interface to pop up (where you can save, load, exit or return to launcher etc)

Also, the game locks up when you exit (only on the pi) does anyone have any ideas what may cause this?

   

We support a basic reasonable mapping of Joystick buttons and axis to the normal Mouse interface expected by the games, but you will likely need to make further mapping to get this working for other buttons. See:
https://wiki.archlinux.org/index.php/Gamepad#Xbox_360_controllers

It is recommended that you either use a Joypad along with a Keyboard or you use a build compiled with Virtual Keyboard support.

I think that lockup occurs if running from command line outside of X Windows when exiting a libSDL application... You should update your version of Raspbian to the latest version and upgrade your RPi firmware with the rpi-update tool to see if that helps with this. See here for further notes:
http://wiki.scummvm.org/index.php/Platforms#Unofficial_Platforms