I don't do sports, but I do remember that sky sports was on in a pub I was in recently with a football game. I don't remember seeing any onscreen adverts (there was the score, the time left, a sky sports logo etc in the corner which seemed fairly unintrusive -- certainly the score and time left are an essential viewing when I do watch England in the finals)
Obviously there's also the adverts around the actual ground, and on the players shirts, most of which seem to be for betting (when I was a kid my grandad put a couple of quid on the pools each week, but this modern stuff seems quite the scourge)
Now at half time sure, they are dripping with adverts -- despite I believe sky sports costing somewhere in the order of £600 a year, and advertising raising just 10% of Sky's revenue from the last annual report I saw.
Were you paying a legitimate provider?