In reply to Kimono:
I was stymied all evening tonight in uploading this afternoon's run.
It only worked when I finally resorted to daring to install Windows 7 on my machine (flawless -what was I worrying about?), and then installed Garmin Express, which seems to be the new version of the Ant thing. Then I used that to upload the run, and it just appeared in Strava. Phew! Before tonight, I hadn't normally had any difficulty, and all now now seems fine again.