British Gas - https://britishgasenergytrust.org.uk/ (not just for British Gas customers)
Citizens Advice Energy - https://www.citizensadvice.org.uk/consumer/energy/get-energy-advice/.
Winter Fuel Payment - https://www.gov.uk/winter-fuel-payment
Help with energy bills: https://www.gov.uk/get-help-energy-bills
The Energy Bill Support Scheme Alternative Funding Scheme (£400), they can apply via this link: https://www.gov.uk/apply-energy-bill-support-if-not-automatic
Alternative Fuel Payment (£200), they can apply through this link: https://www.gov.uk/apply-alternative-fuel-bill-support-if-not-automatic
If you require assistance with their application, please do encourage them to get in contact with the helpline team (open Mon-Fri from 8am to 6pm).
Telephone: 0808 175 3287
Wessex Water - https://www.wessexwater.co.uk/your-account/help-paying