Thanks for that. I ended up having it diagnosed by Ford as a faulty Body Control Module which I've replaced today and sorted the problem. At least I didn't buy another wiper motor for no reason and it seems the BCM does have a constant supply of power to feed through to the wiper motor in the event of this fault.
If I had done my switch idea although cheaper it would have been a makeshift solution and wouldn't have allowed for intermittent wipers + when switching them off they could end up in the middle of the stroke across the windscreen which would be annoying.
I was also able to associate my keys with the new module with the help of youtube watch?v=wyx1WDGNbF8 since they didn't work initially. Strangely when pressing the lock button now it doesn't flash the lights twice like it used to and only lights up when unlocking but I guess that must be a function of the new board.