I suspect the waiting time is due to Openreach. Switching a connection's backhaul probably has some kind of lead time like 10 days.
I expect it goes through a similar, if not the same, procedure as a migration, where the end user has ten working days
to change their mind, (required by Ofcom), and inform the gaining ISP not to let the move go ahead.
This sort of change is in effect a migration between wholesalers, ordered by the ISP.
Ofcom regard working days as Monday - Friday. Lucky them!
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