In message , Mike Tomlinson writes
And responses from uk.d-i-y are an Even Better Thing :-)
Right. You all say extend the CAT5 not the BT line, so that is the way forward. Just to clarify, the main BT socket is in a bedroom. It was in a porch with a leaking roof, and was a mess. The line terminated in one of those brown GPO junction boxes with two rows of six terminals, from there to the main socket, which was unused (who has a phone in a porch?) and from there to a slave socket. When we bought cordless phones, I disconnected the cable from the junction box, and found it was just long enough to enter a bedroom without any splicing, so fed it in there and reattached the junction box and master socket, ignoring the slave sockets.
First step will be to run CAT5 from the router (modem/router/network switch/access point) which will be in the bedroom, beside the main BT socket, outside and down to room containing son's desktop. Once that works, I'll think about a second access point, but having read a little, that involves scary stuff like IP addresses and netmasks and other incomprehensibles.
Of course, this also involves putting plugs on CAT5, which is even more scary. I do have the kit, and even a tester, but last time, it took me about three tries at each end :-)