Ensuite self-catered accommodations are mostly in big hill colleges like South, John Snow, Josephine Butler and Stephenson. The only other option is Cuths (Parsons Field site) but that will be quite a walking distance from the business school. Therefore I would recommend either of the four colleges I've mentioned above. You have the best chance of getting an en-suite in South, John Snow and Josephine Butler. I think you will like being in a big college despite being an introvert, it might be good to try and socialise with people coming from different walks of life. But even if you don't like that, you absolutely don't have to interact beyond your comfort zone! The good thing about big colleges is that there is so much to get involved in so there is a higher possibility of you finding your niche.