The woman is just trying to get off the bill - we were 'too expensive' as well, she has since had some other work done for two thirds the price (boss asked if it was certificated, got no reply, she admitted to paying in cash).
The outside wall is a gable end with the garden down some steps, so garden level below floor level by several feet, I had no reference points to measure up from to drill from outside in, and one point had to end up in the back of an existing socket.
Annoyed.