As soon as I enter that in the terminal it asks for my password then nothing just a new command line appears straight away.
You are entering your password when asked, correct? After that, it should take 10s of minutes before it completes and displays another shell prompt (if I got it right).
Are you copying and pasting the line (there are a number of different quote characters, it'd be easy to get one wrong if you're not copying and pasting)?
What does this give you?
It should give you two lines like this, or is it different?
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 8640920 6298256 1880688 78% /