The threatened closure of the Cally Post Office has aroused local anger.  Paul Convery has sent some material that folk might find helpful if they are writing or campaigning. (these are drawn from full press statements in the word document at link)
Download post_office_protest.doc
Jeanette Arnold, our London Assembly member has said

"I will be making strong representations to Post Office Ltd and would encourage anyone worried about the impact of losing these vital local services to do the same. The Assembly’s Health and Public Services Committee have studied the  impact of the loss of local Post Offices and have concluded that Post Office services must be easily accessible to all communities and extra  protection is needed to prevent closures of branches in deprived urban areas. The Assembly also concluded that Post Offices should be more ambitious and innovative in the range of services they provide, and in the way they deliver services.

The Mayor has said

"I have taken legal advice on the feasibility of a legal challenge to today’s announcement that 171 Post Offices will be closing in

London

and The Post Office consultation. The Post Office have said they will consult for just six weeks over the closure proposals rather than the normal 12 weeks which the Government recommends as a minimum.

‘London’s Post Offices provide vital support for those who are most in need, particularly the elderly, disabled and those with young children. For many Londoners who do not have access to a bank account, the Post Office is an amenity they cannot do without.

Here are some links to post office closure campaigns elsewhere that people might find useful:   very good set of resources here in the otherwise mediocre BBC action network, straightforward factual stuff from PostWatch here, website  This is Money campaign with plenty of coverage, the Lib Dems have a handy campaign site here,

Having had a browse of these sites, it seems clear that the Post Office is using a technique learned from coal mine closures in the 1980s – if you tackle them in small groups, the campaign remains local, not strongly national.