@Leaveitonthefloordrobe I joined Mumsnet this morning to post exactly what you've written, as I am in the same situation.
I've been following this discussion for a while. I've tried many of the tips suggested here (thank you all!) to try and get an alternative to AZ for my first dose but with no success. I've got no walk in centres near me, and my GP is no longer running vaccination clinics, so my only option is the central booking system. I booked one place as I read on another thread that they were offering Pfizer, but I got put in the AZ queue based on my booking, and despite asking and speaking to the head clinician there, there was no way they'd move me to the Pfizer queue.
From playing with the central booking centre options, I have found if I tick that I'm pregnant I get offered centres that aren't available if I'm not pregnant. Likewise I can book locations that I know offer AZ, which aren't available if I tick the pregnant box. I can only assume that based on my age (43), the central booking system won't even let me select Pfizer only vaccination clinics. I've talked to my GP and they say their hands are tied. So I'm stuck with AZ as the only option, despite the data showing the occurence of clots in my age group going up weekly.
So I've done what you've done Floordrobe and have ticked to say that I could be pregnant. My plan is to say, if asked, that I'm hoping for a lucky accident as a last chance this year, but haven't tested yet. I'll have to wait and see what I'm offered at my appointment this weekend.
Good luck with yours Floordrobe, and thank you everyone for the supportive messages on this thread, and the links to the data. I'm the only unvaccinated adult I know, and this thread has helped me feel that I'm not alone and that my concerns are shared by others.