Was he right in refusing to do this please?
Entirely right. The provision task the engineer had received would have had a section marked 'TRC banding' this being the amount of time the CP (Sky) had agreed to pay for additional work, if required, at the customers property.
Very common indeed for there to be no agreed TRC banding on these tasks.
What you were requesting was for the installed to fit additional cabling to make what was previously a completely separate line an extension. Above and beyond, and then some.