I'm back. BT man messed with the cabinet (ah, that's where it is) and then came back and plugged everything in. I would advise you make sure they test all the phones before they leave, because if I hadn't grabbed him, I've have no extension lines.
We did discuss making my office extension the master. He recommended against it owing to it being basic el cheapo phone cable and not the magic cable they use. I tended to agree with him, the phone extension lines are standard builder splice and dice jobs, though they held up OK for ADSL (and the old modem-router hung off my office extension line). My desktop was wired, along with the NAS, and printer, but everything else was on the wifi. The NAS can go downstairs, the desktop can go wireless, and I'll get a wireless print server for the printer.
Currently getting 40 Mb/s down and 18 Mb/s up which is 10x what I had this morning (they estimated 60/20). I suspect it'll be faster with a wired connection (which I'll try later, MacBook doesn't have an ethernet port), this is probably as much as my wifi can handle (with umpteen devices needlessly chattering away and two floors between me and the box of tricks currently located on top of the cats' litter tray). I suspect my wife will pull that face if she comes home to find cat5 cable snaking up the stairs.