The differences comparing to Moscow are remarkable.
First, the borough has bigger impact on the rent rate than other factors i.e. property size and condition. As to Moscow, the only disparity is between central area and all the others, and in London for the same sum (600-650 pcm for instance) one can get a room with shared kitchen and bath, small but self-contained studio or a relatively spacious 1 bedroom (actually, 2 russian rooms) apartment - all depending on the city district.
Another difference to note is that shared flats and houses are much more popular. People can share property for years even being mid-aged professionals which is usually not in option in Russia. At the same time, they don't use to live with parents in London which is a common Russian custom.
City social structure is also not linear - expensive central boroughs are surrounded with cheaper and even slummy ones and then there is a ring of more expensive areas again. So, you can't simply judge by the distance.
Also, every flat has got it's own planning and layout here because typically the buildings are houses intended to be one big property but divided into smaller flats later. Projects and standard houses are either social subsidized or new suburbian development. There is a number of decent and even luxurous ones but not so many to make city's portrait. Typical London house has two or three floors with chaotic entrances, outdoor ladders and so on.