Hi Kat-Kin,
A very good friend of ours (mid 70's) had new double glazing fitted about 3 years ago. She applied to the local council for a grant, she had to pay an amount of the cost (I think she paid a bit more than they required).The council gave her a list of recommended DG firms to choose from, and they submitted the estimates to the council. The council makes the decision of which firm to use, but our friend managed to change their minds in favour of another DG firm who gave a lower quote that was better value for money. The council have put a charge on the property, if she should ever sell it they would be repaid. I live on the Wirral but assume other councils do this.
Jan