For you personally it's true that on current knowledge (and things change every day) you would probably be best off having Pfizer or Moderna to avoid the 1 in a million risk of dying from VIPIT.
However your risk from AZ is hugely outweighed by your risk from Covid so if your choice is any vaccine or no vaccine it makes sense to have AZ if you are over 30 purely from your own personal risk perspective
The government has drawn the line where it has drawn it on the basis of expert scientific advice in line with the WHO and the EU regulator as well as the MHRA and it has no obligation to offer to mitigate a risk for you personally that it deems very insignificant
You are entitled to make your own weigh up but it's not unreasonable of the government not to offer you that choice on the basis of its own risk assessment.
If you feel lockdown does you personally no harm and a 1 in a million risk is not one you are prepared to take them you decline and you wait for your choice to be available or to be available privately.
This stuff happens all the time
There is rationing. We can't always have what we want only what is deemed necessary.
My mums cancer treatment wasn't approved by NICE for her situation. Costs outweighed benefits they said. We accepted that as a family, did our own weigh up all chipped in and paid privately. She died anyway so I guess NICE were right after all.
My point is the government are entitled to distribute a scarce resource as they see fit and they cannot support everyone's individual idiosyncratic choices.
I would have rather had AZ in fact because I am suspicious of big American Pharma companies and the not for profit approach AZ took fits my value system more but that is clearly not a choice that the government needs to support me in so I stuck out my arm and had what I was offered.