We had a great stay at Jen's place. It's located about 10 minutes away from the Colindale station, so it was easy to get to/from the tube. We often came back late at night, and didn't feel uncomfortable at all walking (two women), so that was good! There seemed to be quite a few people out and about even until midnight. The bed and sofa bed were very clean and comfortable, and it was great to have two full bathrooms. We also enjoyed having a kitchen with refrigerator/microwave/sink and dishes to use. We ate breakfast in the apartment every morning to save a little money on eating out.
One thing we did find out the hard way - the flat is pretty far away from the airport. I recommend taking an Uber if you're not going to use public transport, as it's much cheaper than a black cab (less than half the price). Also, the black cab driver wasn't able to find the address using his (old) GPS, so we used the McDonald's across the street as our pickup/dropoff point.