Hi,
The internet cost around £60 for me for the basic package (10mbps download). Worth noting that the wifi is limited to 10mbps, so if you pay for faster it'll only be through ethernet. The wifi is throughout the building, but you can only have two devices connected at any one time, unless you pay a tad extra. Each room has ethernet access (would highly recommend this for your PC/laptop, especially when gaming).
Each flat has 2 toilets and showers, so you'll be sharing each with around 3-4 people I guess.
Congrats on the offer - your summer will be a lot less stressful then most :P