@barry38 Sounds like you already have the answer from the co op. SP and energy suppliers do not get involved with this, you need to speak to installers and government websites Good Luck.
I told my sister about this as she had no heating and husband just had surgery. She filled in the form, rang next day (Thurs) to do survey and check DWP eligibility and have arranged to fit a new boiler on Tuesday. She may/may not have to contribute £200 but this is nothing compared to how much she had been quoted for a new boiler