"therefore, how do they let you know there is a parcel to collect and where from."
Normally carriers will leave a card for you to call them - then you will have to arrange to meet them. Also make absolutely sure you leave a contact telephone number, and instructions, when you place the order - they usually do get through to the driver. Carriers in such countries are well practised in this situation in my experience.
The Post Office usually leaves a card that tells you to go and pick up at the POffice.
In Spain, anyway - It seems logical they would do the same elsewhere.