Result: Unfortunately, I would not recommend a stay at Leslie's apartment, although he seems to be a nice and helpful host. For 1 or max 2 nights the price-performance is ok, but it is hard to relax after a tough day as a tourist.
Pro: Very good and fast communication with Leslie, gave a lot of tips for Malta. Did not use the kitchen, but seemed to be well equipped. Good location, some bars, shops and restaurants in Marsaskala, also a beach near to the apartment, 30 min to Valletta / airport by Bus.
Contra: Flashing/broken light in the old looking bathroom (horrible to have a shower in the evening/early morning). Mattress with metal springs. Just one big light in the sleeping room, just one european (type F) wall socket in the sleeping room. Not that quiet as described (rumour all night long by cars, motocycles, dogs ecc.). After leaving the keys in the apartment, the building door downstairs was locked when I had to go to the airport. As a result of that I had to ring up a neighbour at 4:30am.