Henry's place is okay. It looks exactly as it does in the photos. It's definitely a good price for staying anywhere close to London, but it is a ways from many of the tourist destinations. It is about 25 minutes from downtown as he describes, but many of the 'sights' (e.g. Museums and such) are more like 30-45 minutes away by train.
Additionally, the apartment wasn't clean when I arrived, but that's because the cleaning company that Henry hired cancelled on him at the last minute and didn't even let him know. He rectified it by sending a cleaning company a couple of days later, and refunding my cleaning fee (plus a little extra for the inconvenience). The cleaning company did an okay job, but they didn't do the floors, which was a disappointment.
I am a professional software developer who was working from this apartment for the 6 nights that I was in London, and I can confirm that I had zero issues with the WiFi during my entire stay. Very fast and reliable as he said.
Overall, if you're trying to do London on the cheap, it may be worth giving this place a shot; just be prepared for the apartment to be less than spotless given the unreliability of the cleaning company that he uses.