This evening I made an effort to flex my feet and kick from my hips and keep my legs together and keep my legs high. The instructor commented that my leg action was looking good so my efforts must have been working to a degree. Despite these aims of reducing drag I still found single lengths an effort although I could feel that I was making good progress with each stroke. When I remembered I was also trying to initiate the breathing out period earlier so as not to have too much breath-holding followed by a pant.
There is a lot to think about but I'm beginning to think that some elements of my arm stroke are becoming more automatic and requiring less mental effort to keep them tidy.