Better boilers, mayor sadiq khan's £1m scheme to help people stay warm and save on their energy bills. Maximum thickness of wood surface over the diffusion plate: 20 mm. Any protection you have relies on the provider's solvency – how likely is it to go bust? the risk is minimal with massive energy companies, but if it's a small insurer you've not heard of before, perhaps you should think twice. The customer centre is closed today ahead of refurbishment which begins on tuesday 29 may.