One of my councillor colleagues testified to the London Regional Parliamennts Select Committee regarding the 2011 census. The MPs heard a unified message from Newham, Southwark and Westminster councils about how hard it is to count residents.
Each resident attracts roughly £600 of funding from central government.
Currently central government believes 270,000 residents are residents in Southwark. Southwark currently has 320,000 people registered with GPs. That means roughly £30M of central government grants are not being made to Southwark.
It seems unlikely as planned the 2011 Census will close any of that gap. Worringly it could well open it up further.