There was difficulty in finding the guesthouse at first, but it is actually in Mirador Mansion. Just take the lift to 12F.
A is very responsive both in chat and during our stay, is very attentive, is clear and direct in his instructions and is polite. Room size and cleanliness is actually okay with its price while still being in the center of everything (TST) in HK, so it's really perfect. Plus, there's free hot water and teabags!
I would give it a perfect score review with the given price range, if pillows/blankets have much better scent, and if the TV is also working. Overall, 4.25/5. I'm hoping to go back to HK in three years and I would love to stay here again.