Your criteria for making your decision i.e. "5 days of annual leave which I would sooner use on the water" is not sound. We would all like to spend our time on the water
as opposed to at a desk. But it is not a logical way to think about the issue. The RYA make it clear that the best way to complete the course is to do the theory first, then the practical. It stands to reason. You can apply your theory skills to the practical exercises, during the practical course. If you don't have your theory properly embedded, you can't execute a host of tasks in your practical course with any competence.
The notion that the instructor can teach you theory during the 5 day practical course is simply, wrong. My experience from students who do the NavAtHome course is that they feel they could do with tuition that is more "present", or having a tutor at hand. However they all report that they like this method because they, like most of us, are "time poor". They also report that for all its drawbacks (which aren't many), it is a great way to complete the theory course, and probably the best way. By applying a little discipline, i.e. say just 5 or 6 hours per week, you should be able to knock it off in say 12 weeks. Try 10 hours per week!
I think with a wider sample size than CF (large though it is) you will find the vast majority will recommend NavAtHome. With this under your belt you will then find yourself having some fun as you learn what the practical course was designed to do....to teach you the practical components.
A useful tip, when buying
the books, is to buy the eBooks through the RYA website, not Amazon. The eBooks can then be used on a number of devices as opposed to one. Become an RYA member
and you will then be eligible for discounts on a plethora of their products.
To answer the question above about "which books", start with The Navigation
Handbook, The Weather
Handbook and Day Skipper
Shorebased. But even better just go to their website and cherry pick all the topics that interest you in addition to these.
By the way, I am in no way connected to NavAtHome.