I’m not sure if this is specifically the area of the Wildlife Trust but as your website says: “Influencing the land-use and marine planning systems to make sure that house-building, gravel dredging and other activities don’t harm habitats and wildlife.” I thought it was worth a go.
I live in an area of Southampton called Lordswood (SO16 8EJ) , it’s a nice place, and, as the name suggests quite woody, full of trees and wildlife. The area has little signs around it saying that various areas are “managed to encourage wildlife” (see [http://www.southampton.gov.uk/s-leisure/parksgreenspaces/thehawthorns/wildlife.aspx]), though most of the time these would appear to be ignored
From what I’ve seen in the past it would appear to impossible to change any of these decisions after they’ve been made, but I enjoy the small forest and marshy area (some of the proposed site) and I like hearing the owls, the bats, the woodpeckers and seeing the nuthatches hop up and down the trees.
As I said at the start, I don’t know if this is something that you do, or if there is anything that you can do, but any support from the HWT would be very welcome.