Somebody may be able to clarify - but I believe the little strip of forecourt outside shopfronts, which one often thinks isn't actually public highway (like here), generally falls within the domain of the local authority, who levy a charge on the shopkeepers if they want to bring their goods or tables & chairs onto it. Either Lewisham council or the police, or both, should be able to enforce against this type of parking, whether the vehicles have road tax or SORN or not.