having done a boiler service,i gave the usual visual on the other gas appliances,duty of care and all that , this is a house split into two flats up stairs and downstairs,noticing the black sooty marks on the top fire, i asked when it was last looked at, this is an elderly forgetfull owner who could not remember i advised on getting it serviced and fitting a co detector,he accused me of making work for my self,i was a bit taken a back by this and more or less told him" i've advised you,it's up to you",.the thing is i feel as if i should have done more and i have a feeling the down stairs property is on the same flue as the up stairs flat,i have tried to phone the daughter of this elderly man,she arranged boiler service but can not get back in touch ,what more can i do ,or what would you do