I sympathise with your sleep issues. And because of that I was just about to mention the flight path. All three of the areas you mentioned will suffer from airplanes ever 90 seconds or so, depending on the runway alternation (the rotating runway schedule). You will want to research this if you are looking anywhere west around the river, especially if you have sleep issues. And when you are looking for flats, try and do so on a day when the alternation is happening so you can hear/judge the loudness for yourself.
I lived further west on the flight path (Richmond) for a couple years and the only time it really bothered me was when it started up early in the morning just after 04:30, but I almost always fell back to sleep. We lived in a big block with single glazing, so it was a bit louder, however we had really thick window coverings, a fan with a towel over it for white noise and I wore ear plugs. Still heard the planes. It was more annoying on the weekends when we'd go have a pint on the green to watch the cricket with giant 747s flying overhead. Not completely peaceful considering the idyllic village.
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That being said, all three areas you mentioned are fantastic. I really like Clapham Old Town - it's really quaint and quiet, like its own little village and a short walk from Clapham Common Station. There's a Marsh & Parsons there that will work hard for your business. Sadly Clapham may have good transport links, however it's a bit of a pain to get to Chiswick; there's no "easy commute" that doesn't involve multiple changes or venturing into zone 1, upping the cost. Unless he gets a bike, of course.
I second Hammersmith. Take a look at Brackenbury Village, W6, the area bordered by Padenswick, Glenthorne, Goldhawk and Hammersmith Grove. There is a fantastic pub called the Anglesea Arms that's on the Ravenscourt Park side of this neighbourhood. Highly recommend a visit if you are perusing the area. Brook Green is also lovely, it straddles W6 and W14, on the other side of the trainline from Brackenbury Village to Kensington Olympia. Walking distance to Westfield and High Street Ken and numerous transport links for an easy commute. Rents are higher in these areas, but I think you can find something for £400/wk.
Parsons Green is my fave part of Fulham so take a look around there as well. When I was looking there I personally thought the planes were too loud for me, but I am super hyper sensitive to them now. Thanks a lot Heathrow.
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