A picture is worth a thousand words....
Hi Paul & welcome aboard.
Go with the new Self-Coached Workshop Perpetual Motion Freestyle DVD. I began with the book & the older Freestyle Made Easy DVD.
The book is a help for reference & for understanding the actual mechanics of efficient swimming but if you are beginning this journey on your own you will find the visuals of the DVD far more beneficial.
The drills & methodology have been updated to make everything clear & concise, I purchased it recently & it is worth the price. In addition you can download the user manual from the website so that you begin on the right foot.
You may have limited practice time, but if you focus on doing what you can well in the alloted time you have in the pool rather than the number of pool visits then it wont be long before you begin to see some really satisfying results.
Hope this helps, good luck on your journey.