I think you were right in your first post Aruna.. I read the lines you quote as meaning that Mr and Mrs Jennings lived and had friends near his business in the City (not a smart area - much despised by Miss Bingley!). After her husband's death Mrs J moved to the more elegant area around Portman Square. I rather suspect that her daughter Lady Middleton may have been instrumental in persuading her to move away from her old haunts to a smarter part of Town.

To help people get their bearings a map of London in 1810 can be seen at:

http://www.bl.uk/onlinegallery/onlineex/crace/s/007zzz000000006u00192000.html

(Sorry to make you all copy & paste - I still haven't mastered the art of making embedded links.)
Click on the "Interactive Zoomable Image" icon.

The locations which concern us are all north of the river. The old City of London is to the east (right) of the built-up area; it is outlined in red and tinted pink.

The part where the rich and fashionable chose to live is roughly the western third of built-up area. Oxford Street cuts straight across this area from west to east. Portman Square is a block or so to the north of Oxford Street and just three blocks from the westernmost edge of London.

Later in Ch.26 we learn that Mrs Jenning's house is in Berkeley Street.
I have put a link below to a picture of the north side of Portman Square published in 1813. The red houses visible in the distance are in Upper Berkeley Street. The road which runs east from Portman Square is Berkley Street , which was built around the same time and would have been similar - not as grand as the houses in the Square itself, but nevertheless, a very elegant area indeed. No wonder Elinor was content with Mrs Jennings' style of living!

While we are looking at the map, some other locations in this week's chapters:-

Willoughby lives on Bond Street, which runs south from about half way along Oxford Street down to Piccadilly. This is smack in the heart of the luxury shopping area - these days Willoughby would undoubtedly have a wallet full of maxed out credit cards!

The Palmers live in Hanover Square, which is just south of Oxford Street and one block east of Bond Street.