The first allocated flat to me was not the flat listed in the listing on Airbnb; and that flat is not so great as it is in Ground Floor with a long flight of stairs to go up to the 2nd floor room and also hard to open windows and broken shower head in one of the washroom.
The check in process was easy, not so much of hassles, just following the instructions would be able to get in the flat. However, the Emergency contact in the envelop has no one to answer; perhaps it's because my check in day was a Sunday. I can reach no one when I check in and found that the apartment is not the one listed no matter how hard I try.
On the following day (A Monday) - I have been able to contacted Airbnb and the Apartment staff; they have arranged a change for me . After moved to the higher floor apartment, with all rooms in one single floor; everything was amazing. The flat is with a nice patio facing the church, ventilated well with lots of windows. The apartment is clean and is as nice as shown in the posted photos. You have everything you need from cooking utensils to bathing gel and towels provided. The living room and dining room were really comfy. The kitchen is very well equipped, you have washing machine and disc washing machine and oven. The bedding and pillows are also comfortable. The shower from both bathrooms are great with strong and hot water.
Location wise, it's right next to the regents park so it's lovely to visit the park every morning. There is a bus 88 right downstairs in few mins walk brining you to the central area such as oxford circuits. 10 - 15 mins walk is needed from the apartment to the nearest tube stations (Great Portland Street / Euston / Warren Street / Regent's park). You have many lines to choose from, and easy change to rail at Euston.
There are also some grocery shops right downstairs of the building in the opposite road if you need anything.
After all, if the upper floor flat is arranged, everything is great and amazing, and I would come back to this flat for sure next time if I visit London again with my family. Special thanks to Sasha helping to arrange the change of apartment and help me to get back my left item after check out easily.