It very probably is correct - they know about boilers - they set their own rules and for H&S reasons will not want their staff putting themselves in danger by messing with asbestos.
You may have a case - I would make a big fuss to get my money back - you have paid your monthly service bill in good faith and they have taken your money - now they spring on you an unfair contract condition - taking your cash under false pretences.
It is not reasonable to expect a householder to be aware of the construction details and materials used in a boiler - SWALEC are the experts here - the least they can do is to pay you back.
Good luck...
Peccavi, February 2011
