" I think perhaps the thing that is bothering me is that AA doesn't seem to advocate doing a half programme, in that I've been encouraged to immerse myself in it and follow the steps properly."
my personal view is that doing a half programme is an excellent strategy for anyone who successfully worked a "half programme" on drinking.
However, there are as many interpretations of what a "full programme" is as there are members of AA; and, as you will know by now, the ONLY requirement for membership is a desire to stop drinking.
I know people who do not work the steps; people who do not share; people who do not have a sponsor; people who do not do service; people who refuse to acknowledge any Higher Power except, perhaps, AA itself; and who are nonetheless long-term sober.
I think, in all their cases, the key fact is that they ARE working a full programme in that, whatever they drop from the "textbook" approach apparently being sold to you, they replace it with something else - in my own case, I can't get to a lot of meetings, but posting here helps plug that gap a bit. Likewise, people (again like me) with no sponsors who nonetheless remain sober will typically allow themselves to be sponsored by the group, in other words talking and sharing and listening in meetings and picking up the experience of others that way.
I would only describe as a "half programme" something that misses out one of these concepts completely, e.g. you don't work the Steps but nor do you go to meetings (steps 1-3), share at meetings (steps 4-7), put out your hand to the newcomer or the sufferer (step 12) and so on.