I know, quite well, a student who lives on board at Sawley. His boat is 40' and he is on a leisure mooring. Technically, he has to leave or take the boat out every four weeks, but this is easy to do: he only has to take the boat a short distance away. His total costs, as he's told me are considerably less than staying in student digs or residence halls, and he's adamant about this. Also, he can go home during university term breaks so this shortens his overall stay at the marina, and of course, it reduces his utility costs. I should think that a 30' boat could be just right for you, and that could give you a mooring fee of ca £1500 p/a. I'm a research fellow at Nottingham and I stay at Sawley on a leisure mooring, but I'm only there for ca two weeks at a time, followed by two weeks at home in Wales and so on. I live on a Norman 22, and I've found it comfortable (the electricity for an oil filled radiator is quite cheap!). In fact, if you want inspiration on living in small places, I recommend that you google sites on van living, tiny houses, and shanty boat living; also sites that deal with living aboard sailing boats. At these types of sites you'll find a very broad range of people's experiences dealing with 'small space' living.
I recommend that you go down the boat route, it will be cheaper than digs. If I had to take a room in a house in Nottingham/Beeston, it would cost me about £60 per week (before utilities). That's more than £3k p/a and three times my annual mooring fee. Go for it, it's totally doable!!