My throat is very dry and no matter how much I drink it remains dry and my nose feels blocked however when I blow it noting comes out what cud this be?

Nasal obstruction . It is likely you have a nasal obstruction that is causing you to be a mouth breather, particularly at night. This can make the back of your throat feel especially dry. You should see an ENT for evaluation of your airway and the cause and treatment of your obstruction.
Its your nose. The constantly stuffy nose leads to mouth breathing which in turn leads to your dry mouth and throat. Fix your nose and the mouth and throat improve. Allergies, chronic infection, anatomical blockages all can be involved. As an ENT doctor i think starting with an ENT evaluation makes the mot sense.