It depends, from uni to uni, precisely what is or isn't included, but as a general rule the utility bills (heating, lighting, water, hot water) tend to be included in the cost of halls (though some places will, for example, charge extra for excessive use). In the specific example of Exeter (since I'm guessing that's where you're talking about from your location and the third-party accommodation providers you've mentioned) these bills are included in the charge for the nominated residences you're talking about; internet's extra, though.