Don’t know an awful lot about the freight side, it’s UPS SCS as it’s known now, a lot of it is similar to most freight operations, collections from suppliers to warehouses (Costco, Amazon, Argos etc) as well as in and outbound freight from the airports, some of this will be fed to the hubs while some will go direct to customers.
Feeders doing the night trunking are hands off, they don’t touch anything, trailers are loaded and unloaded by the depot/hub staff. They don’t even seal them, it’s all done for them, responsibility is on the warehouse staff not the drivers. The hubs and the newer depots have extendable conveyors to load/unload, you can walk to the front of the trailer and press a button and the conveyor will extend the full 40ft. Pre-load shift at the depots starts around 3am, first trucks arrive anytime from half 2 onwards.