My thanks for
all the replies and advice.
I am familiar with the browsing history ads, some showing sites I have visited and others offering products and services that are "interesting and eclectic"....
...and which I get bemused at as I have never actually sought such products.
I do, from time to time including today in fact, also get a caption on here and on the BBC / Met office sites saying, for example...."bbc.co.uk is not responding"..so I press the refresh button and the page is restored.
The Met office site in particular seems to coincide with the loading of the various commercial adverts the site now carries.
Non of the above may be in any way related to the issue I originally asked about of course, but, for those who know about IT, may possibly be aware of some form of common issue.