Hi, sorry, been away from the boards - bloody real life!
We saw CIO really as a stage in the CC process to be honest.(If you leave them for 10 minutes and they have gone to sleep then they have cried it out - it is just timing rather than leaving tham and moving to Hawaii!)
When we first started sleep training we were swadling DS still (arms not feet- and, yes, later then HVs tell you) which was helping his sleep but our intervention when he woke was to re-swaddle - immediately. From there it was a case of leaving him for an interval before intervening. Then it was going in but not re-swaddling (that had become his new sleep association). Then the intervals of going in became longer until he actually fell asleep. I think his longest was an hour but I'm sure it must vary.
Certainly I was aware that me going in to him would invariably "re-set" him because he would get very hacked off at me going in, not picking him up and then going back out again. Otherwise, you are not leaving him for an hour - you are leaving him for 3 20 minutes sessions (for example) and gaining nothing. Thye just get frustrated that you are not doing anything!
Sitting outside his door and rocking dementedly was my mid-way concession!
Even now, if he is ready for sleep he wants me out of the way! (illness notwithstanding, obviously).
I'm sorry it is proving so hard with your DS but it does take a while for new habits to bed in. If you are satisfied that he is not hungry/ill etc etc then yes, the best course of action is still to ride it out at this stage. Don't do your initial "check" if you can avoid it otherwise that will simply become part of what he expects when he wakes.
Hope you have had a better night since. x