Does its job

@narinder912 Thank you.

To nitpick, there is no logo in the header but just my site name in text. But this header design is acceptable out of the box. Its better than the bad logo presentation I was getting from the tagdiv AMP plugin.

A logo is displayed if you select a Site Icon in WordPress: https://codex.www.ads-software.com/Creating_a_Favicon#WordPress_Version_4.3_or_later

Note that we’ll likely switch to using a Custom Logo if it is available: https://github.com/Automattic/amp-wp/issues/975

See also https://github.com/Automattic/amp-wp/wiki/Legacy-Templating-And-Customization#logo-only

I have also managed to add Google AdSense by inserting the ad code in the ‘single.php’ and the linked script code in ‘html-start.php’. It is also possible to add some text and links in the footer (footer.php). All .php files referred to above are the plugin’s own files and can be accessed by going to Plugin Editor.

You should not be using the plugin editor to modify the files. They will get overridden the next time the plugin is updated. To modify templates, you should copy them into an amp directory in your theme and then you can use the Theme Editor to modify them safely.

Thanks for your quick reply @westonruter
Will try to do as you suggested.