My family and I spent 4 awesome days at the apartment in Mellieha.
Stephen and his dad Daniel were a great host. Stephen was very responsive and helpful in all his emails with me and his dad met us in the centre of Mellieha to show us the apartment.
The apartment itself was great - very spacious, very comfortable and very clean. It's built on a semi-basement level of the house Stephen lives in, so getting in touch with your host is literally a matter of walking up the stairs. It's about a 2 minute walk from the central cathedral of Mellieha (which is as downtown as you can get for Mellieha). The closest beach was a 10 min bus ride (bus stop across the street from the cathedral). If you're looking for a place walking distance to the beach you might want to get something outside of Mellieha, but otherwise it was pretty convenient for exploring the north of the island.