Postage Pro UK has a perfect, total privacy policy. The application never asks for any personal details, and never sends any information you input to the internet.

Postage Pro UK Free and Many Stamps are supported by you, by choosing to purchase the Postage Pro UK paid version.
It's recommened to check the application permissions of any app you install.
Postage Pro UK / Postage Pro UK Free and Many Stamps do not request the permissions to scan your text messages, phone storage, contact list, or enable your (battery draining) GPS.