this is a "for information" post rather than a question.
I have a home office at the end of my garden, while my broadband connection (FTTC) is at the front of the house. The office is connected to an Ethernet socket inside the house next to the incoming master socket. An external cat5 data cable runs round the outside of the house to the garden then runs underground to the office, terminating in another Ethernet socket in the office. Total length of the run is about 230ft.
The router in the house provides Wifi, plus wired connections to the TV, Xbox and an Ethernet power extender to provide Wifi in the kitchen. The final Ethernet connection on the vendor router is then wired into the socket for the office. At the office end the cable is taken about 2 feet to a DLink 9104 WAP which gives me wifi in the office and a wired connection to my PC.
Reason for the post is that this setup worked well with my BT service, using their standard home hub (I think HH4, anyway, the one before the current one as of this post - I'd had the service several years). However, despite being a customer for a long time, BT's pricing policy meant that I switched to VF Unlimited Fiber 76 service recently.
All went well, service was on at 08:15 (against a plan of 08:00) and speed etc was good, so the main house was all OK. However, the office was completely dead. After a lot!!!!! of messing around on my part, a friend who knows about networking inserted a small 4 port D-Link switch between the new VF router and the socket in the house leading to the office, which solved the problem.
Reason for the post is to highlight (as others have done) that the VF supplied router is very poor and so hopefully this may help people who may want to set up something similar avoid a lof of head scratching/ time and frustration.