One of my machines has failed twice in downloading the Windows 10 update. I have downloaded and installed all the 'old' windows 7 updates as I wonder whether it needs to be up to date first? Who knows.

If you look in Control Panel - Windows Update - Update History it should tell you if it has yet tried (and perhaps failed) to do the Windows 10 upgrade. It looks as though it first started trying to download it on 28/7/15.