Sorry, Frank, I don't have a VRBO to recommend in SW7 (South Kensington). Wish I did. But here are several apartments with which I was very happy, just in case you are unable to find one in SW7. Check out the London School of Economics: http://www.lsevacations.co.uk/
They offer apartments or suites, with a kitchenette and coffee maker, laundry room in the basement, and some locations have a cafeteria on the first floor. Look at their website for more information; they have several locations, all convenient to the tourist sights and museums. Different prices for different locations.
http://www.lsevacations.co.uk/Home.aspx#sthash.IAOqSaYR.XEd3XAf6.dpbs
Here are my favorites; Grosvenor House Studios, Northumberland House, Passfield, and The George IV Apartments.
http://www.lsevacations.co.uk/Accommodation/Northumberland-House/Northumberland-House.aspx#sthash.XHS1Hx8u.dpbs
Grosvenor House is located in the Covent Garden/West End area. Easy access to restaurants, the theatre, and transportation:
http://www.lsevacations.co.uk/Accommodation/Grosvenor-House/Grosvenor-House.aspx#sthash.2FnVbjCG.dpbs
Passfield has a two bedroom flat:
http://www.lsevacations.co.uk/Accommodation/Passfield-Hall/Passfield-Hall.aspx#sthash.lDvrscG1.dpbs
The George IV Apartments also offer flats:
http://www.lsevacations.co.uk/Accommodation/TheGeorge/The-George.aspx#sthash.Zwp3eF7v.dpbs
I have stayed at all of these locations. You will have to call the phone number for each location to check for availability/vacancies on your desired dates. Be aware that the website DOES NOT show true information about availability. If you try to check that online, it always says they are full. Not true. You must phone to check.
Also, they offer student dorm rooms to tourists when students are on break. But that is not what you're after. They all have the apartments and suites on the top 2 floors; that's what you are looking for. Keep looking on their website if you don't see that right away. And make it clear that's what you want if you call their phone number and book.
I was very satisfied with all of these locations. All comfy beds, living room, kitchenette. Price was right.
If you wish to stay south of the Thames, look at the Bankside House, which is near the Globe and Tate Modern. I realize these are not in the SW7 area you asked for, but they are comfortable, affordable, and well located.