Extremely friendly, helpful, accommodating staff. The apartment we stayed in is well furnished and maintained. We love the coffee from the lounge. Breakfast was good, not a wide range but of good quality. Although the nearest tube station isn't that near but the walk to the nearest tube station (around 10-15 mins) is a very pleasant walk. The bed is a bit small though and we agree with Marianna15 that the hot and cold water in the bathroom is very hard to adjust.

Overall experience; well above our expectations.

Obviously these apartments are in Mayfair, so they are expensive. You are paying for the location. It was nice to have an apartment, which gives you a bit more space. We had a two bedroom apartment. The L'Occitane toiletries in the bathroom were a very nice touch. Our main bathroom was small but clean and everything operated efficiently. There is a shower within the bath tub. In the second bedroom, there was a very small shower only, which did not have great hot water coming through. It is roughly a 7 minute walk to Green Park Tube, or a minute or two longer to Bond Street tube/Oxford Street. We walked to our Theatre in Picadilly in 15 minutes. The furnishings and TVs appear a bit dated. The king size bed in our bedroom was extremely comfortable but the air conditioning unit appeared to struggle to cope. We stayed here in September and the room was quite warm, so I wouldn't like to see how the air conditioning dealt with summer. I was not able to utilise the free internet service to check my flight times because it crashed everytime I tried to get into the Singapore Airlines site. It was extremely slow and I gave up using it. The female staff member who greeted us on arrival was friendly, as was Alex and the other male staff members. My husband experienced an unfriendly attitude from a female staff member. Whilst things feel a bit dated, I felt quite comfortable here.

I wanted to give this hotel a 4 and a half star rating in this review, but since i can't do that on this website, i decided it was leaning more toward a 5 star rating.
Postive Things:
-The staff were excellent-- warm, friendly, and always cheery, i would like to give a big thank you to Marguerita and Franscesca.
-3 minute walk away from some nice breakfast eateries.
-More than anything, this hotel is really like a home away from home. Although we often stay at other hotel brands such as Ritz Carlton, Four Seasons, Hyatt, etc. we decided to stay here due the scandalous price of hotel rooms and suites in London and also the tiny size of the rooms even after paying such a high price. And i have to say that some, and only some, of these hotels are a bit too posh to the point of feeling uncomfortable, and the Ascott Mayfair really made us feel at home.
-The blankets and quilt was amazing.
-Taxis pass by the hotel often.
-There is a church right around the corner.

Negative Things:
-The room, we stayed in a double bedroom apartment. We have a few complaints about the room. First of all, i don't see the point of having such a lovely thick blanket/quilt when the room itself only has a tiny and completely useless aircon. Secondly, there were just a few tiles missing in the floor. Thirdly, the TVs, which they have now changed to flat screens, are tiny, a bit too tiny.
-Location, although this is in one of the most expensive areas of London, it is nearly a 7 minute walk to the nearest Tube station(Green Park Station)! And we had to take the Tube very very often because taxis in London are very expensive.
-Although one of our rooms had a view of a lovely park, the other room had a view of a brick wall.

N/A things: We didn't eat at the restaurant because for breakfast it was 24 Pounds for one person.

Overall: Although the room was just a bit disappointing, the staff were great.

We stayed in a studio Standard room for just one night, the size was good (for English standards) but the bed was very small, I would say 1.40 m. width most, so the 2 of us could barely turn on the bed.
Fully equipped kitchenette. Another issue was the faucet in the bathroom, it was very hard to adjust the hot and the cold water to a normal temperature.
The breakfast which was included in the rate was very good, good variety and tasty.