This is related to another thread titled: Windows 7 will not update to SP1 - 0x800B0100
Thanks Richard (niemiro). I solved it before I got your reply.
For my scenario, I had no errors in the SURT log file, but the Fix it mentioned in [Windows 7 will not update to SP1 - 0x800B0100] thread did not work for me (although I didn't try it in Aggressive mode, because until you replied I did not know how to do that).
Turned out to be McAfee real time protection. I switched that off, and voila SP1 installed fine.
Hope this helps someone.
Kevin