Home Run (www.ueastudent.com/housing) is the accommodation service run by the Students' Union at UEA. They have a section dedicated to incoming exchange and Erasmus students on the website above, along with all their contact details. You can also ask them (or Google!) for details of letting agencies within Norwich, however do note that almost all letting agencies will charge a fee, and some are better than others!
Also, please do feel free to use the Facebook group to form housemate groups, and then look for houses together - especially if you are looking for a whole academic year, it will often be easier to find a three- or four-bedroom house for a group of people than it will to find a house with one room going spare, or where the landlord lets the rooms individually.
Finally, always be very careful. Beware of anyone who is reluctant to let you view a property or show you pictures, avoid sending money until you have seen some sort of contract and some photos. Ideally it's best to always view a property in person, but of course that may not be possible! Most importantly, never send any money via cash transfer schemes such as Western Union - anyone who asks you to send money in this way is almost certainly a fraud and should not be trusted.