My grandparents had a pleasant stay in this flat.
It was clean. The communication with Timothee was perfectly fine. He answered very fast. The self check in is very easy.
It was a good location for us, since I don't live far away. But if you want to visit the center, be aware it takes some time to get there. 10 min by walk to the next metro station and then another 10-15 min by metro. For us absolutely fine though. Also you have the beautiful Parc Elisabeth and the basilica close by. The Atomium isn't far neither.
The flat is located under the roof. Which means you have to go up some stairs to enter the flat. Not the best option for small kids or elderly.
I found it a bit strange that they expected us to put towels and bed linen in the linen basket and to do light cleaning before leaving. It's not that it's too much to ask, it's just strange. I never came across something like that.
Overall it was a good stay.