(BC) Child Passport renewal in Pakistan

My wife and children who are BC, are stuck in Pakistan due to Covid etc. My son's (5.5 years) passport is due to expire on 13 November 20, can someone please assist with the queries below:

1) experience of renewing British passport in Pakistan, what is the usual timescale.
2) Would we need to send the old passport as supporting doc for the renewal application? i am in two minds as, if they are able to fly back before the passport expiry, the old passport will be with the application and he will be stuck there. On the other hand, he cant get back before 13 Nov 20, we need to have a renewed passport in hand before 13 Nov 20.

Passport renewals from Pakistan can take anywhere between 8 or 16 weeks to 6 months or sometimes longer