I've followed this thread - it has to be said with some incredulity - and at first didn't believe it was anything other than a wind up.
Of course PPs are right that OP does have a choice: she can choose to take the vaccine she's offered, or not to take it. And if she's adamant she wants a particular vaccine (none of which the law of averages suggests are risk-free, and all of which will have a low number of serious effects), then the option is to wait until it becomes available and, possibly, to bear the costs herself.
OP complains about the way this crisis has been handled. To an extent I agree: but the vaccine rollout is one thing the UK has got entirely right. We are world leaders in this respect. Bad publicity for one particular vaccine is crassly irresponsible scaremongering, and those responsible for doing so should hang their heads in shame.
I acknowledging OP's response isn't ideal: the sense of entitlement is sometimes reprehensible and she certainly should not be wasting appointments in this way. But below the aggression in the OP's posts is the emotion that's really driving them: fear. It's also grief. Neither emotion is conducive to rational decision-making, and the whole thing has been blown up into an enormous issue in the mind of someone who's already struggling.
OP - I'm very sorry about the loss of your brother. If you feel amenable to this, you might benefit from some counselling to enable you to separate out the different effects of this awful loss on you. I've been bereaved and know the terrible effects it can have.
Try to stop reacting in panic, as your actions can have real repercussions on others who might be desperate for that vaccine. If it will set your mind at rest, try to attend a vaccination centre you know to be offering an alternative (you will likely not get Pfizer).
FWIW yes, I've already had one dose of AZ.
I wish you the best.