DCLG has carried out an assessment of proposals to remove householders’ permitted development right to pave over their front gardens unless they use porous materials. The consultation paper says around two-thirds of London front gardens are already partly paved over and the highest proportion of paved front gardens is in North East and South West England where more than 75% are paved. It says impermeable hard paving blocks cost £8-17/m² compared to permeable at £15-17/m².

u http://www.communities.gov.uk/publications/planningandbuilding/permeablesurfacing