The part required will depend on what's broken - your boiler engineer will be able to determine this within an hour or two and be able to work out the make & model of your boiler.
British Gas will want to put in a completely new boiler for a few thousand pounds so it may be best to avoid their services. A few (very few) boiler engineers are out to make a fast buck - be cautious of any engineer who claims that two or three different and expensive parts all failed at the same time - a remote probability.
Yellow Pages or personal recommendation for a tradesman.
Good luck...
Peccavi, October 2009
