You can have the second AZ jab before 12 weeks I heard this morning, as early as 8 weeks.No. Against considerable evidence to the contrary I still believe in altruism. The sight of others behaving selfishly doesn't really alter that feeling.
I think it's in our DNA whether we feel it or not.
Though less frequent, the most uplifting chapters of humanity have come about through altruism. If we're ever going to be anything but automatons in a game theory view of life it's through altruism and putting one's immediate interests second. (By contrast there is no end of examples of what pure self-interest can lead to.)
TBH I don't think it will make much difference in your case anyway. Your hesitancy is only about AZ not about whether to get vaccinated at all.
So have you calculated when the likely date of your second injection will be under each scenario? I expect it will depend to a fair extent on whether the government can adhere to the promised dates for abundant Pfizer, but if they can then I suspect there wouldn't be much difference in the two completion dates. Perhaps only a few weeks - not really enough to matter much to the grand timetable for Phases A, B, C and D of the National Cabinet roadmap.
That of course is only looking at it in terms of when you complete your vaccinations. Getting your first jab earlier (ie with AZ) does bring forward for you and the community a modest level of protection / reduced risk. You don't get as sick as you might otherwise be, you're less likely to take up a hospital bed and the likelihood of you passing it on is reduced. That of course will only be relevant if we have recurrent outbreaks, but that's looking more and more likely.