How much ‘rental’ did you pay BT for your several extension sockets in convenient locations ? , absolutely nothing is the answer , yet strangely you expect that to be kept operational or supplied with something that can replicate it to a certain extent, but why , your extensions etc were your property not BT’s , and you could have simply adjusted that to work with the router , basically the extensions wiring connected to the router rather than a socket in the wall …if this were to ‘complex’ for a DIYer (it’s not ) then a contractor could have be employed to do this ….that is exactly the reasoning Sky , Vodafone and others took , there was no obligation for BT to supply anything , regardless of anyone’s sense of entitlement.
You calling PSTN an ‘analogue’ phone system is something of misnomer it’s been a digital switching system for over 40 years , the analogue interface to the ‘line’ was simply to maintain legacy devices , and the ‘works in a power cut’ was never a design criteria, it was the limitation of the technology from 100+ years ago that necessitated having the ‘central office’ supplying the power , again maintaining for as long as it was , to ensure backward compatibility for devices, eventually 40 years old tech requires replacing.
