Southwark Council has carried out "huge change" to it's systems at HOU for notifying and billing leaseholders with new approaches kicking in late 2012 / 2013. Including "automated" systems. The extent of the mindless automation we're still trying to find out about.
Southwark Council over a decade has shown as disturbing incapability to introduce new semi-automated or other systems without serious teething troubles.
Whatever, it can no longer be the collective delusion of leaseholders that for some demands for payment, received by some leaseholders, the Council failed to include a "Summary of Rights" leaflet (or otherwise inform of Rights) and therefore the demand is not payable.
This is in addition to other issues with validity of invoices and demands for payment.
Southwark Council Leaseholders may want to check carefully that bills / invoices / demands they have paid were actually valid in the first place.