The setup is different on FTTC. BT Openreach do the installation and provide a VDSL2 modem. This has to be close to the master socket, where they fit a new filtered faceplate. If you go for BT Infinity then BT Broadband supply a (cable version) Home Hub. With other ISPs you can buy a suitable router from them, or buy one elsewhere as I did.
Your new router doesn't need to be next to the modem, but connects to it with an ethernet cable. So you can't use your existing 15m one that way
. What sort of cable is it exactly? (Thinking of post-installation solutions).
What may be a possibility if it is a good quality extension cable is that the engineer might move the master socket to the other end of it, and use another pair in the cable to get a phone signal back to the existing position, with a normal socket. Note I say "may be". Very possibly he won't - let's see what others think.
Have you ordered FTTC, or just thinking about it?
My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost
. Internet connection -
IDNet Home Starter Fibre.