Reading Google's Web Master Guidelines at https://support.google.com/webmasters/answer/35769?hl=en it seems they place a lot of emphasis on how fast a site loads. This is not surprising as these days, your typical human browser is not willing to wait longer than a couple of seconds for a web site to load before losing patience and going somewhere else.
I spent the next 2 days or so implementing all these changes and managed to get the speed up into the 90% band for desktop sites and 75% for mobile sites. I then waiting about 2 weeks whilst monitoring my sites rankings and waiting for the improvement in speed to be reflected in increased rankings. However, nothing happened. I was rather disappointed. Making my site more like Google would like it to be should be reflected in web site rankings you would think? Apparently not.
So now I shall downgrade web site speed in my list of priorities for my web site and instead keep my focus on content.