Looks like GAME Eastbourne (and probably others) are having a sale on Xbox One bundles.
They just tweeted:
"LTD time ONLY we will be selling #XboxOne with #Forza5 GOTY for £299.99! CRAZY,but I think we can do better than that! come into store!"
...suggesting that they can either do a cheaper price, or add some other item(s) into the bundle.
Link to twitter: https://twitter.com/GAMEEastbourne/status/547052251978940416