Log in failure to BBC account following Safari Upgrade

I updated to Safari 12 this morning and now I can't sign in to my BBC account. When I click "Sign-in" the progress bar goes across the screen but nothing happens. As a result I can't watch catch up (iPlayer) on the iMac

How can I resolve this?

Thanks

Message was edited by: *****@ me.com Updated to increase detail and correct OS

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