More about Northumbria University
If you son does quit before christmas, I believe that he will only be charged for the first semester. However, if he stays till after christmas he will be charged for the full academic year of university study.
Your son also has a contract with accommodation, if he does drop out (even if he moves home) he may still have to pay for the full year of accommodation unless him/the accommodation can find a replacment to take over the tenancy.
Univeristy can be a massive change, if he has not settled in well or looking to drop out. I would advice him to talk to the library services, lectures and seminar teachers about his best options.