I had BT Infinity installed recently and had exactly the same situation as you - a 70s bungalow with the master socket next to the front door. I say master, but it has no NTE5, just a standard telephone socket. When the chap arrived to perform the installation, we "walked" the route to where I would like the modem to be installed. It involved a data extension kit and, since I had the floor up for other work, it was all put under the floorboards to a more convenient place next to a 4-way mains socket for power. The installation was tested with the Home Hub 3 router in the same position, but I later put the router in my study and ran a 20m Ethernet cable between the modem and router (again under the floorboards).
Whatever you do, don't be tempted to link them with Solwise Ethernet over mains units - you will lose about 75% of your speed!!!
My installation has been rock steady since the install and subsequent "stretch" between modem and router and today the bRAS rate was 38,710 measured.
During the install, the Openreach chap swapped the incoming socket to an NTE5 with the word Openreach on it. It also houses the filter.
All in all, a very happy bunny here ...... and a high-speed one too.
Colin