Depends how far into Norfolk you are I suppose but if I was anywhere in East Anglia I definitely would go to Sovereign Quarter Horses in March.
David and Sarah Deptford own it and are 2 of the nicest people in western riding. They also have a massive indoor school and good lesson horses.
We go there for shows and it's three hours plus in a lorry. Any closer and we would go to ALL their clinics. A FAB place!