Well, moving the TP-LINK router across by two fairly thin-looking walls (about 6m) bought us another 6 or 7dB in the back rooms, & maybe 5dB across the highway, but moving it as far as 25m further on didn’t help the back rooms at all (probably even cost a few dB), & bought across-the-road maybe 2dB if that.
So... Mr TP-LINK will be sitting next to the TV (flat on the wall with antenna sticking straight up) & we’ll probably get another router to plonk across the road as a bridge.
It does leave me wondering whether the original router site somehow formed a wireless black hole, though.
Oh, I notice that Mr Shuttleworth found a way to fill up the Gutsy DVD, specifically Win32 versions of things like Firefox, ThunderBord & AbiWord. No OpenOffice there, but I guess asking for an extra 150-oddMB for that & a few localisation packs turned out to be a little over-hard.