Hiya,
You'd be comforted to know that rental yields in london as of the moment are lower than other luxury areas. Example: Chelsea, Regent's Park, Notting Hill. House prices are finally softening!
I found this great resource. http://www.globalpropertyguide.com that helps much with property investing overseas. According to them, the highest yields in London can be generated from 100 to 150-square metre flats, reaching up to 5.36%
Good luck to you
