Hi Neil,
may be try reboot before you run the commands again. Lets disconnect the PC from the Internet. Turn off all antivirus / antispyware / firewalls etc...
Also make sure you right click on the Command Prompt icon and select Run As Administrator before you type the /wuforce command..
from the command line change to the directory that contains the file you just downloaded and type WindowsUpdateAgent30-x86.exe /wuforce
Fingers crossed
regards
Steve