If you are ex Navy sir, then you already have the discipline required.
As a beginner, should I concentrate on 'Hands Separate' initially or should I be trying to get both hands working together right from the start?
You should get the hands working together from the start, but also practice often with separate hands. There was an old school of thought that recommended learning each hand perfectly before putting them together, but it has been demonstrated that this is inefficient. Here's an article about hands together/separately: https://trainingthemusicalbrain.blogspot.de/2012/03/hands-together.html