How can we even be sure the BARB are accurate anyway? From what I've read in various articles etc they are out by 3-5% on a regular basis. I would personally take Sky's figure as they will be able to track a lot more accurately the amount of viewers watching there channel.
On top of these figures I doubt they take into account pubs and bars that have the games on as you cannot accurately predict the amount of people in each establishment. I am also interested in the figure, is this individual households that had the program on, because you cannot accurately represent the number of people in a household watching a channel. You've also got recorded copies watched later, plus people who stream illegally
If you took everything into account the real number would most likely be a lot larger than the figures presented.
...AND FINALLY...from someone I know who works for Sky in their IT department; the BARB cannot track things such as live tv through games consoles accurately and the Sky Go app etc. Therefore I would take anything presented here with a pinch of salt and more importantly I would choose to just ignore "William Eve".