The Wolfson Foundation is one of the UK's largest independent funders of capital projects. Its Funding for Places programme names places of worship as one of its categories, alongside education, heritage, health and the arts.
Grants start at £15,000 and fund building refurbishment, restoration and equipment. A church heating project could qualify where it forms part of a wider capital improvement to the building. The Foundation runs two rounds per year with a two-stage application process, so plan ahead: it takes around five months from first application to a decision.
For listed churches needing fabric repairs, the Foundation also runs a separate scheme in partnership with the National Churches Trust. These grants of up to £10,000 cover structural work such as roofs, floors and drainage. While not aimed at heating directly, churches combining a heating project with fabric repairs could use this alongside other funding.