Mmm, this gets weirder by the minute!
Its now working fine for me (with the favicon) in a “Private” window in Firefox … but still not in my main window! I’ve tried clearing cache, rebooting, etc etc… but still the same
Well, I guess as long as its working ok for others - I can live with that! I was just concerned it was putting people off making purchases, as the padlock wasn’t showing up.
Thanks everyone for the help / suggestions!