Thanks for your reply, but not really relevant to the problem.
Manually placing a SPP file or it's contents into the VCRM repository folder is not going to fix a download issue.
However, I can confirm that some updates I manually placed in the folder are being added to the VCRM software list.
Virus Scanner has been turned off to rule that out. Disk space is not an issue - I did state that I tried this from multiple locations (i.e. different servers physically located in different locations).
Again, clearing the VCRM repository folder is not relevant to the problem.
Both the server and VCRM have been restarted with the same issue.