To cut a long story short I needed to ensure that the following lines were present in public_html/php.ini
extension=pdo.so
extension=pdo_sqlite.so
extension=sqlite.so
extension=pdo_mysql.so
Setting up VirtualBox
In Settings/Network select Bridged Adapter if you want to be able to connect to the vm
In Settings/Display increase the amount of video memory
apt-get update
apt-get upgrade
apt-get install dkms
reboot
Then use the file manager to select/mount the additions so that they can be installed