A user visiting a space is equipped with a mobile device in communication with a service system. Media items held by the service system are associated with various locations around the space and a user arriving at such a location is presented with the corresponding item or items. Preferably, these media items are preemptively loaded into a cache of the user's mobile device in dependence on the user's progress around the space. Items can also be flushed from cache on this basis. In order to reduce load on the service system and the related communication infrastructure, a media item needed by a mobile device is first sought from a nearby device using a short-range communication mechanism.