sub-post office
From Longman Dictionary of Contemporary Englishsub-post officeˌsub-ˈpost office noun [countable] a small British post office that has fewer services than a main post officeExamples from the Corpussub-post office• The judge also said staff at the Berkshire sub-post office may never recover from the terror of that day.• For example, why can not every rural sub-post office have a vehicle relicensing facility?