A delivery and collection system comprises a plurality of automated locker assemblies, each comprising a plurality of contiguous lockers which are monitored and controlled by a central computer system. Each locker has an autonomous lock unit including a processor, memory and short range wireless transceiver which communicates with any of a plurality of mobile phones or other wireless devices. Customers of the system are granted access to the lockers by validation codes which are communicated via an enabling message from the central computer system to an app running on the customer's device. The app is configured to send an access request to the lock unit based on the enabling message, and to transmit event details downloaded from the lock unit back to the central computer system. Each enabling message may authorise the user device to perform multiple deliveries or collections or may be a one-time code.