Yes - Powerline adapters. I have disabled on the PC in question though and just use the 5Ghz WiFi

From the Vodafone help site If your connection is provided by Cityfibre you would get the synchronous 100/100.

However if your connection is openreach the 100/20 would be correct.

Ours is through OpenReach so the upload speeds are < 20% of download. I am OK with that,