HomePod is Stuck on HomePod Beta and Won't Restore

Yesterday I was having problems with my Apple ID on my new iPhone and Watch and my HomePods started playing up. The HomePods were on 8.1 and I have been unable to restore them.

They go through set up but when I get to adding iCloud I just get error 41 and have been told it cannot do it.

Apple Support can't help as they were on Beta. I am trying to restore a HomePod via my Mac but when I click on restore it just flashes.

Can anyone advise how to force my HomePods back from 8.1 to 8.0 or how to get them to restore/set up?

Thanks

Angus