I didn't stay at Asia Cozy House, as my room wasn't ready when I arrived (despite booking an extra night, and fore-warning the owners that I would be arriving after midnight, they seemed unaware that I even had a booking).
This review is instead for Charming Hotel Hanoi, as that is ultimately where I ended up.
It was fine for a no frills, budget stay. Cleanliness could be improved - towels and sheets were stained, but there was a lift for luggage and WiFi was good upstairs, spottier downstairs. Room size for both the twin and double rooms were good for me as a solo traveller.