For Foodstuffs, submit List Price changes through NPC/Rapid (these should always start on a Monday date, with limited exceptions). You'll then need to complete the Supplier Price Adjustment form in the Foodstuffs eXchange 'Products' section and ensure you submit that form through to FOBL. The NPC price data will help automate this process.
For Woolworths NZ, submit price changes through both the National Product Catalogue and ProductFlow (GS1 simply carries out some basic checks that price is present/available to Woolworths).
Version 1.4 – Updated 20th January 2021