Slightly off topic I know, but you can just imagine the carnage there will be trying to get a lot of 'older' folk off the PSTN to VOIP based setups. Especially those with no broadband currently (of which there will be quite a few I'm sure).
It has not just been imagined, it has been trialled in Salisbury (FTTP) and Mildenhall (FTTC), and it's being rolled out nationally.
For those with no broadband, new SOGEA and FTTP products with 0.5Mbps up and down are being released.
Certainly, the CP will have to provide a router, and someone will have to plug it in, and plug their phone into the router. For those who aren't comfortable doing it themselves, I expect assistance will be available.
I would compare this to the TV analogue to digital switchover, and that was completed successfully.