I can definetely recommend a stay at Mario's Apartment. Location and style are just fantastic. Taking into account that there are only few sandy beaches in Malta it's even more amazing that Mario's place is directly at the beach.
As the owner himself was abroad when we stayed in Mellieha his very kind friend Grace was there for us. She even hand over the keys at 1 am as we arrived very late.
It must also be mentioned that Mario always replies very quickly.