An update to this. The only thing I had left to do seeing as the problem was unique to Chrome, EE and this specific PC tower was to fully uninstall Chrome and all user settings and reinstall it. I did that a few days ago and it's made absolutely no difference . I still get the 10 second delay on loading some web pages. I've watched the 'network' tab in the Chrome page inspector and it is *exactly* 10 seconds whenever it does it - never 9, 8 or 11.
I did some experimentation with a free VPN extensions in Chrome. If I have TouchVPN extension running and connected to their UK VPN, the problem fully goes away. I am of course fully aware that using a free VPN offers no privacy whatsoever but as there is no noticeable reduction in internet speeds on a speed test, it is proving to be a Heath Robinson work-around to the problem until the true cause can be ascertained.
Small update of sorts. The issue seems to have fixed itself without me doing anything which is quite bizarre. It feels like it has happened gradually as I don't recall a day when it suddenly went from a 10 second delay to none at all. As mentioned up thread, I was using TouchVPN extension in Chrome with their UK server and it allowed all pages to load instantly. At some point the 10 second delay must have stopped happening as I haven't needed to use the VPN extension for a couple of weeks now. All pages are now loading instantly directly on the EE 4G connection and working as it should!