Also I know the download speeds for files are shocking on Virgin using the XBOX. My friend who's on BT fibre uses wireless, I use wired 152mbps. His max speed is in the 70s. We both hit download at the same time. He downloaded the game 15mins quicker than I did.
I'm sorry to hear you're suffering from slow downloads on your Xbox One. Do you have any way of testing your Xbox One's connection speed as gds1972 has done? I'm curious to see if the download speeds you're getting from the store are drastically different from the connection speeds the console is recording.
I'd recommend also trying a wired connection test to ensure this issue isn't being caused by wireless interference.