Update from me:
No dice on AZ. I had discussed with my GP and went to the appointment (at a different clinic, as my GP surgery was not in the current rollout) - I had a discussion with the GP who would be administering the dose. He asked why I wanted it, what I knew about the pros and cons and read the letter from my doctor. He said he would do it if I pushed for it, but wanted to know more about my work. We discussed my work, and given that I work on a regular basis with those of our most vulnerable (elderly, disabled and homeless) he advised I was actually eligible for Pfizer in the current rollout. He asked if I would consider not getting AZ yesterday, and get Pfizer on Saturday. I was totally fine with this - I figured it's only a few days and then a shorter period between doses.
So, Pfizer on Saturday and again in 3 weeks - same time, same station. To be honest, I'm glad I was able to discuss the matter with the GP and he really genuinely listened and took the time to go over it with me. And I'll be fully 5G compliant in a shorter timeframe.