ECO4 application - difficulty getting evidence

BlissC

We currently have a very old gas boiler (40+ years) which needs replacing as it doesn't meet current gas regs and the heating system keeps malfunctioning. I've been advised to apply for ECO4 as I'm disabled (a wheelchair user) and have limited mobility. We don't qualify under the income criteria (our household income is just slightly too much) but I've been advised we should be eligible under the 'NHS route' (Route 3) as I have limited mobility, for which you need proof such as a letter from your GP. I'm not on Universal Credit, but I do get the PIP high rate mobility component, although PIP isn't a qualifying benefit. The contractor has provided a template letter that explains it all, quotes the NICE guidance on it, and all the GP needs to do is tick the relevant box and sign it.

I put in a request with my GP practice, explaining what it was for and that I have a template letter, etc...the response I've just received from the surgery:

"This request has been reviewed by the GP Partnership and this piece of work is something the Practice is not able to provide or complete. This does not fall under the NHS contract nor is this something the GP Partners are willing to offer privately for a charge. We are sorry we are unable to fulfil your request. In this case, we would advise you contacting a service such as Citizens Advice for support with this." 

Where else am I supposed to get proof from? (my health problems are long term and I'm no longer under the care of any hospital consultants, just my GP). Has anyone else had difficulties getting the required proof of a long term condition affected by the cold/limited mobility for ECO4?

Thanks, 

Bliss