I would approach this with caution. I have been offered external wall insulation under green deal. Six months ago my council blanket visited all the houses in my neighbourhood heavily pushing external wall insulation.
. However the approved contractors for my council are completely useless. After signing the various contracts / grant forms and arranging a fitting date, they realized that they can,t actually fit external wall insulation to a house with bay windows – this is after 2 surveys and 3 visits when this problem was not identified. F***wits.