Claim it's a welfare case. Elderly, disabled, carer, home worker for key organisation, just use your imagination but has to have ring of authenticity to it.
That's not me as that would be disingenuous, hence I just accepted the delay at the time regardless of the big inconvenience to us.
In our case it's due to the sensitive nature of a job role - hence the FTTP was ordered as an additional connection alongside the existing FTTC to facilitate home working with separate connections (required by company policy). Not having the additional connection resulted in no home working - hence my comments about the Openreach blanket stance not taking account of individual circumstances. I even asked about having an additional FTTC connection instead and they still said no.
Anyway - that's all irrelevant now as the restrictions have been relaxed and just need them to come and install it!