Chimney's need to be swept at least once a year if burning wood. https://www.findachimneysweep.co.uk/
The Home Energy Saving Advice Service on 0300 123 1234 if you are in England or Wales.
If you are based in Scotland, call Home Energy Scotland on: 0808 808 2282.
If you are in Northern Ireland, please call 0800 1422 865.
The National Insulation Association (NIA) has a list of approved installers. The NIA postcode locator tool is at the top of their website: