There is at least one - the Hilton DoubleTree Milton Keynes is located in the West stand of the 32,000-seat Stadium MK! (Home to the MKDONS)
Several of the room types feature views out over the pitch (you'd want the ones saying "With View" in the booking list), and the restaurant/bar has views out of the pitch.
The only downside is that the executive rooms are generally unavailable on match days, as they're used for hospitality, and someone on FT mentioned that not all of the fitness facilities are available on match days as apparently they get used by the teams!
The hotel is also only a short distance from Bletchley Park, which is a must-visit for any crypto/spy/code-breaking/computer/history geek, and you can often get some stunningly good advanced-purchase deals at the hotel for weekend stays :)