Is there a grant or help with financial cost for a leaking false chimney that is going to cost around £1500.00 to fix. I am on income support.

I would love to say there is, but you are in the UK and this is an international site. I am in Canada and if I had that problem I would have to hire someone to fix it. All depends on how much you value your comfort. Shop around in your area and see what you come up with.