Since January 2013, external wall insulation on individual dwellings has been classed as an alteration for the purposes of 'permitted development', meaning planning permission may not be required. For blocks of flats and certain dwelling types, however, planning permission will be required.
View information on applying for planning permission. The planning portal website gives information on the types of measures that will or will not require planning permission, depending on different conditions. You will need to check whether you live in one of Ealing's conservation areas.
For information on requirements of building control with regard to energy efficiency improvement measures, see the building control pages.