Hi all
Thanks for taking the time to respond to this. I had another look at it with a fresh head this evening and found id made the simplest of mistakes. i had not named the machine properly in virtualbox, which then wouldnt allow me to create a new virtual disc and finish the process of adding the VM to virtualbox (although it looked like it was added and was in the list)
@Niccea the reason i thought there may be old files is because it was telling me there may be, but it looks like that was because it was trying to install onto the same virtual disc as an existing linux ubuntu VM, because i hadnt been able to specify the creration of a new virtual disc for the install. (i think)
Thanks again for all your responses, problem is now solved. Lesson learned!