Thanks for your reply, I was actually in the process of doing this. It has now downloaded but when I double click on the downloaded file I get this error:
'The following disk images couldn't be opened:
Reason: Illegal seek'
Is there something else you're supposed to do to then get the software to update one this has downloaded rather than trying to open it like you usually would open a downloaded item?
Any help would be great, this is driving me mad!!!