So all halls are different, if the hall is catered there aren't any proper kitchens, just small kitchenettes, and those tend to have more students in a flat, like around 20.
Most flats have around 5-10 people
You'll have your own space, it's not really that common you'll be sharing an actual bedroom with another person unless you choose to do so, and your room will have a lock and key for it so it's all secure
Unless you have an ensuite (these tend to be a lot more expensive) you'll be sharing a bathroom, but you should only be sharing with like 5-6 other people depending on how many bathrooms there are and the size of the flat
You'll most likely make friends and meet people easier if you live with them, otherwise you're limited to the people on your course