So I had my brekky and sat down at the 'puter. Clicked on the email button and it said "No, does not open". Clicked a few more times, restarted and it still wouldn't work. So I went off and got my swimming stuff out for this afternoon and when I came back and clicked it just opened as it did yesterday.
Phew
And AARGH, now it is Lloyds Bank that isn't working
A number of hours later and it just works again.