On the advice of the lovely @Delatron I used C:19 for our antigen tests to go to Greece tomorrow.
Spectacular balls up on my part, entered my dd DOB wrong, massive panic when checking confirmation email and spotting mistake but easy to go back in and resubmit - then three hours later got an email from them saying that the passport pic I had attached was for my other DD - blood pressure through the roof!
Resubmitted for third time - certificate in ten mins
Absolutely 1st class service! I've been trawling these threads for advice for weeks so thought this useful to share. Hopefully this time tomorrow will be in Crete!