Glow-worm - www.glow-worm.co.uk

BPEC - bpec.org.uk

Corgi Gas - corgi-gas-safety.com

CITB construction skills - citb-constructionskills.co.uk

City and Guilds - city-and-guilds.co.uk

EAL - eal.org.uk

Institute of Plumbing and Heating Engineering - iphe.org.uk

LSC - lsc.gov.uk

Worcester Boilers - http://www.worcester-bosch.co.uk/homeowner