I would totally read the hypothetical fic in which Mitchell becomes aware of his attraction to Brooker through his strange compulsion to watch mock-masturbation clips, I have to say. Thank you for the reassurance!

I've often felt surprised that I've not just hit more buzz about it

You're right: not only is there little fanfiction, but few people even speak about it in a fandomish way. It is odd and slightly frustrating. Peep Show, as I understand it, is quite popular; surely some of its watchers must be in fandom.