@David-TP Thanks for your reply David! 

So, what I have done this morning is speak with Vodafone again, via Live Chat, to verify the details I was sent yesterday via SMS when I spoke to them on the phone. They do match (although the support agent gave them to me in COMPLETELY the wrong order/format).

So, then I went onto my router and went to the Status page where it lists the "Local network MAC address", I confirmed that this matches the MAC from the bottom of the router on the sticker too. 

I re-entered the user/pass in Deco under the PPPoE settings, I setup the VLAN 911 with priority 0 (as numerous people mention) under the VLAN ID, leaving IPTV disabled (is there anything I need to do here??). That didn't work, so then I did the MAC address cloning, entering the MAC matches that on the bottom of the router... that still did nothing.

I'm really struggling here and unsure what is going on. I couldn't get the credentials to work on my desktop PC when putting the WAN cable directly into my desktop either.... I set the user/pass and it wouldn't connect.

My connection is "serviced" by Vodafone but is a City Fibre installation.

Thanks,

Simon