Figured out the answers to my own questions...and learnt a bit of CLI along the way 
So the figure quoted in the above table is FREE Disk Space! I'm going to mod the script to include capacity and free space and perhaps even provisioned.
In order to only report on Storage that VM's were using (SAN Storage and not Local) I changed the following line from;
$Datastores = Get-Datastore | Sort-Object -Property Name #| Select-Object -First 1
to
$Datastores = Get-Datastore -VM $VM | Sort-Object -Property Name #| Select-Object -First 1