For me it took the love of another person and the birth of my son (but even then I was still using til a month before, that's disgusting behaviour

shows you how fucked up that shit is mate, be realistic about how hard it's going to be for starters).
Maybe it's a case of starting simple, write a list of pros and cons, this works for most things in life I find.
But yes, you do need to speak to people...try NA sure, but why not the doctor? If not your local drug clinic? You can get counselling, support and keyworking from them which doesn't have to involve methadone or subutex. You in London at the moment? There are a load of places and whilst they are full of junkies and script seekers, there are plenty of good staff who want to help you. All of that relapse prevention stuff, be it 1on1 or group based is fucking bollocks to begin with, but it might be just what you need, and you have a massive plus point, you actually want to quit, I think?
Sounds like you can't do it on your own through the traditional routes though chick such as distraction, activity, exercise, good diet, change of circumstances etc etc. So you gotta reach out, this place is a catch 22...and if I'm being honest initially it's best avoided.
Bon chance