To clarify, the 5.1 audio is only working on the Netflix app. But it worked immediately with Dolby audio selected in the VFTV menu (Settings->more settings->audio & visual-> select dolby audio) and when playing netflix content, arrow up to options/audio & subtitles/ select english original 5.1 - although this was selected by default I think.
The Netflix app is one thing that is great about the newish Vodafone TV. We don't have a smart TV, so having the app saves sending it to our Chromecast through a phone.
I will be calling Vodafone Support and asking for a refund and reporting them for breach of contract. Vodafone website stated that it works till it was highlighted in this thread and then they changed the wording. I logged a call 12 months ago.