That seems fairly likely, there's been a few bits that are very similar to the documentary. The bit where the interviewer/Theroux stays in the mother's bedroom in Scarborough with the wardrobe full of clothes for example.
I've got one episode left to go, but so far it's been pretty well done even though it's not a particularly enjoyable thing to watch. Brave move by Coogan to play it, but he pulled it off I reckon.
I read a review somewhere that the interview for a book aspect of it could have been based on the Louis Theroux interview. Would be interesting to go back and watch that, how much was said or hinted at... I've seen it, but don't really remember it.
No, it wasn't Theroux, although someone said the same earlier in the thread. The character was a real reporter called Dan Davies whose story is accurately depicted. As a kid he was in the audience on fix it and formed a relationship with Savile as an adult where he interviewed him numerous times with the intention of writing a biography.
I thought Coogan''s impression was good but he slipped into Paul Calf several times when he was trying to be funny.