I hate to say this but your right..
"heaven sent" sounds like the opening but it's not exactly like it..
I have one for about 3 minutes and a few seconds long but I noticed that it's not the same thing(even though I am watching it in spanish:S)
It has to be remade since the intro of heaven sent is like a 1 note followed by a 16th echo delay and again and again witha different note, whil the opening theme is just like Synthesizer strings....
(which I would prefer to get that instead:()
the only hint I have to do is watch the ending credits....)
email me if you want to hear..I could try and send it via email:(