" Unfortunately we have bank holidays and weekends in the way of this one"
Yes - though I'd been assuming it would be a 7 day a week operation. (Just as I think testing carried on over Christmas Day and Boxing Day?!) Given current conditions, I'd be surprised if they weren't trying to achieve that, even through Bank Holidays. (Not underestimating the logistical difficulties, pressures on staff and so on. Definitely a case for paying double-time, bonuses etc, although I realise that doesn't address the stress.)
Allowing Pfizer second dose is a good point - though that will be an ongoing issue, I assume, as Pfizer will carry on alongside Astra Zeneca.