Trimingham is a village and a civil parish in the English county of Norfolk. The village is 5.9 miles (9.5 km) north of North Walsham, 6.3 miles (10.1 km) east of Cromer and 24.8 miles (39.9 km) north of the city of Norwich. ~Wikipedia
Local historian Dot has informed me that this is the location of the old post office shown on the postcard. She also told me that it has been in 9-10 locations over the years.
I found this interesting genealogical page which refers to the Postmaster and Postmistresses.