I also have 2 Pfizer shots, and went to Royal Garden Plaza 2 weeks ago for my booster... They told me because I Had Pfizer x2 I could not get a Pfizer booster, which is all they were offering.. 😔
I'm in Thailand and therefore haven't had my booster in UK but I guess you just need to show proof of 2 jabs whether they be 1&2 or 2&3.
When I did my Thai Pass I used same cert twice for each upload. If you can crop the qr code and upload also you might get an instant approval..... Worth the extra effort..
Never had my passport details on the vaccine certificate and was not a problem. Rgds