Wow you have done a really good job - no wonder you are exhausted. You must be relieved that the home is not the problem. I agree that a GP visit is a good idea because it would give you a chance to talk to him/her build a relationship and I haven't heard of the CNM being so involved either - but you could make it clear to the GP that your Mum isn't happy with her and neither are you and then the GP may well take back the primary care position.
From everything you have said I don't think you are wrong - your mum was clearly in pain and that was causing agitation and it will take a few days for her to settle back onto the codeine. There has been a move away from codeine I believe for patients where it was prescribed but something less would do the trick so perhaps that was the thinking behind it (combined with the out of date meds lol).
So pleased the oils went down well so now it is your turn to pamper yourself and get a good night's rest so that you start to feel much better too
Sleep well, well done xx