Ditto for local residents. I don't think Kinko's charge much for a few hundred A5-sized flyers to be printed, which can be leaflet-dropped into local residents postboxes to make them aware of the next protest.
I second what James and Martin said. Really not rocket-science to publicise something like this, which, since it depends on good turnout to be effective, is a pretty crucial thing to organise. Leaflet drops don't take long if the work is divvied up amongst some volunteers...
While I'm pleased that a website has been set up, it needs a bit of tweaking. I'm not sure if you helped build it or have simply passed on the link, so these comments on the site are not necessarily directed at you.
This page: http://savepottersfield.org.uk/2.html states that Berkeley Homes want to demolish the former school and its annex. This is not my understanding of the proposal, which is that it seeks to demolish only the annex. If I'm wrong, my apologies. Otherwise it needs correcting, or the error damages the campaign's credibility.
The 'Mission Statement' on this page: http://savepottersfield.org.uk/3.html does not display properly on my Mac, with most of the text invisible and all squashed up. When I did manage to extract and read it, it describes the concerns of the community, but does not express much of a positive vision for the site, which is what most people would expect of a 'mission statement'. If it is not possible to agree on a single vision for the site (which is quite understandable) then something short and snappy like 'Our mission is to prevent the development of blocks of flats on this site and to get Southwark Council to run an adequately funded public consultation programme to establish what the public would like to see happen to this site.' The rest of that material is background stuff which belongs on the 'Profit vs People' page: http://savepottersfield.org.uk/7.html
Personally I do not really like the grey concrete image as a background and the sort-of graffiti in the top right hand corner is very distracting, but that is simply a matter of taste. As long as the text and images are corrected to display properly, the rest is far less important. It is good that the site is up and running, in any case.