Chelmsford is my home town and my immediate JW family is still there.
Like Sabin said, it's a wealthy to middle-class, growing town which has recently acquired city-status. Definitely on the up. It also has good transport links to the south east of England and London and is on the right side of london for the ports and channel tunnel.
The site they have bought was previously used as a scrap-yard, as I understand it, so a lot of the land is contaminated (so I'm sure they got more for their money). The construction has local political support because it will improve what was an eye-sore and hazardous area.
My old congregation is heavily involved, with some of the brothers dedicating the next five years of their lives and careers to the construction effort. Families are hosting brothers that come in from elsewhere to help with the project.
On top of that, last year the Chelmsford congregations acquired a new building which will house their new kingdom hall right smack bang in the centre of the city and work has been going on all year to kit it all out. I understand it's due to open for the first meeting later this month. My family tell me a its a big facility and will be used for local JW schools such as for pioneer schools, elder schools and so on.
So there is a massive amount of excitement and activity going on in the Chelmsford area for JW Land! They are in uber spiritual paradise! ;)