I spent one month at Mark's and even tho there were other 5 people living in the house, the place was always clean and quiet - no dirty kitchen or bathrooms at all. Flatmates were super welcoming and respectful of the house as well as each other spaces and times, I definitely had a fun time around them.
You can hear planes flying over pretty often, but it's not a big deal and after 22 they start flying higher, so no problem for sleeping or working from home at all. Mark did a good job keeping the house clean and tidy and was super responsive if any issues popped up. I'd not recommend the double room for staying more than one month tho, especially if you're a couple. Your best option for longer terms is the bigger room at the top floor which is bigger and gives a bit more privacy.
It's a no smoking house, so if you do smoke you have to leave the place every time and basically go across the street - but again, not a big deal.
Location is well connected to the center, has a cool pub at 2 minutes walk from the house and a wide choice of supermarkets at 10 minutes walk maximum. If you're after partying hard you're really - really - close to both Clapham and Brixton, which surely offer more than Stockwell does.