They got lucky with 1914. Even so, they were predicting their big send-off for October. Not August.
If you want an insight to the fears current in England, there was a whole stream of invasion literature written from the 1870s onwards. England gets invaded by the Germans, mainly, with the odd French invasion when there was a bit of friction before the old Entente Cordiale. The most famous example, however, involved Martians on the loose in London... But all part of a very long period of fears and tensions leading up to the war as the problems between the so-called Great Powers increased and the arms race escalated.
Trying to be kind to the WBTS writers, they can't even quote their own literature correctly from the time period so I have no doubt whatsoever they haven't a clue about this.