On 30th May 2013 the Government brought in amended planning legislation, for a temporary three year period, which relaxes the permitted development rules for certain types of extension.
A notable feature of this relaxation is that homeowners are now allowed to build larger single-storey extensions to their houses without obtaining full planning consent. In summary, if you live in a semi-detached or terraced property, you can build out by 6 metres from the original rear wall of the house, and if your house is detached you can build out by 8 metres, subject to certain constraints. Different rules apply in Conservation Areas.