Right, sorted the problem with USB.
For some reason beyond me, adding the user via the user and groups GUI is not working at the moment, At least for Virtual Box. However, doing it the traditional way via the terminal does work.
Open a terminal and type the following:
sudo usermod -a -G vboxusers user
Where"user" is your actual user name
So, for example, mine would be:
sudo usermod -a -G vboxusers stephen
Then log out of Ubuntu Mate and then log back in. Then open Virtualbox, fire up your VM and right click the blue usb icon at the bottom right of your VM window. You should see your peripheral USB device listed. However, let me know if not.