If you run a radial between all the secondary’s, there’s a choice of two that can be the master.... one at each end.
Actually, the master can be at any of the points. You can wire two wires into a standard punchdown terminal - so can run extensions off in two directions.
kind of old fashioned having a load of phone points. I bet the homeowner ends up with DECT phones and a bunch of empty phone sockets
But as a late friend of mine was fond of saying, better looking at it than for it. It's easy to not use sockets that are there, it's "a lot harder" plugging into a socket you want to use that isn't there.
'very long time' is a bit of a stretch when the current target is for the copper network to be taken out of service in between 5 and 7 years time.
As already said, that's just pie in the sky thinking - not a snowball's chance in hell of it actually happening in that timescale. If they were serious about it, they've be pushing fibre right now - but as it is, they still have pricing (e.g. for FTTPoD, that's on demand) that seem designed to avoid anyone taking them up on it.
It is now only 2 & 5 that are used the wiring of terminal 3 is known to cause interference and affect ADSL broadband speed
No. Current designs of filter plate split out the DSL signal before filtering the voice signal and splitting out the ringer line. So it's safe to wire pin 3.
If BT fit an NTE5c+VDSL Mk4 filter it is possible to wire from the filter to an RJ11 extension socket or module for a VDSL hub / router to be located away from the NTE5c ( master ) socket at a more convenient location.
Doesn't have to be those, many older designs also have terminals for the A&B wires. One way of doing it is to use (e.g.) the green/white pair for the DSL and link that pair behind the extension sockets until you get to the one where you want your modem - then you fit a BT+RJ11 socket and don't take the DSL signal any further.
At my parents house when I was still living there "some years ago" we added extension sockets (as well as more mains sockets, aerial etc) as we redecorated. I put a 201C box under the stairs, routed the incoming line down to it (honestly, the master socket moved all by itself
), and then radially wired out to the extensions. I put a filter on the master socket, and only ran an unfiltered line up to my back room where I had the router.