Mike Barnes :
I'm following up my own posting to thank everyone who's responded and clarify a few things. Sorry not to reply individually but there's so much overlapping information that this way makes most sense to me.
I know some people like to go to town on their video systems but TBH I can't see that happening here. We don't watch TV at the moment and I can see this system being used for the occasional film on DVD or whatever or so that visitors can get the sports results, but not much else. There's another room for listening to music, with the obligatory monster speakers and cables. So I'm not looking for ultimate quality or something I can upgrade for fun, just something that works and doesn't look too conspicuous. Having said that surround sound would be nice and AFAICS won't be terribly difficult.
Regarding the height of the speakers I'm tempted to put them on floor stands with low-level outlets so that the height is adjustable and the stands will mask the leads.
I do like the idea of mains cable for the fixed speaker wiring because it's thin (especially if removed from the outer sheath) and it's manageable. The walls are plastered, but unfortunately the plaster is stippled. I wouldn't have chosen it but I can't be arsed to skim it all over so it's staying. I'm therefore looking at speaker wiring behind the skirting boards, or possibly on the floor next to the carpet grippers. But what sort of connectors would you expect to see at each end? I know wire binding posts would be cool but I'd prefer a plug-in connection.
Knowing nothing about modern TVs I assumed that the topology would be like a PC, with all the intelligence and connectivity in a table-top box, and a screen that's *just* a screen with only two connections (mains and video). Looking at ads on the internet though, it seems that everything tends to come in one lump and if you want to put your screen on the wall you have to run all the bloody wires up there as well. Have I got that right?
As I said I'm looking at a screen location in the centre of a wall. The room is littered with obstacles (two external windows, one internal window, fireplace, central heating radiator) so there isn't a great deal of choice. The location I had in mind is on chimney breast, and yes, the fire will be used. I don't know whether that's a bad idea, heat-wise. The fire is a cast iron wood-burning stove entirely contained within the fire opening (the front of stove is behind the plane of the wall) and the flue is lined so it could be worse I suppose. Looking on the bright side, there's an alcove to the left of the fire, 500mm deep, which would be ideal for the equipment cabinet, which I'd buy if possible or make if I can't find anything suitable. And if the wiring is in a surface conduit I could route it up the side of the chimney breast and sneak it round to the screen quite inconspicuously. I haven't decided on a screen size yet but 60 inches isn't out of the question and would just about fill the 1500mm width of the chimney breast anyway.
Height-wise the fireplace containing the stove is only 800mm high so the screen wouldn't have to be particularly high off the floor. At the cinema I like to sit on the front row so I'm used to looking up! If rising hot air is likely to be a problem I might well fit a "decorative" shelf below the screen to deflect it but that wouldn't add too much to the height.
The other possible location for the screen is across the corner in the aforementioned alcove but that would limit the screen size and I don't know how the surround sound would work with the screen in one corner and viewers in the opposite corner.
Thanks for all the ideas, my thoughts are focusing nicely. Ideally I would spec out the equipment now, but I'm putting that off for as long as possible.
One last question: satellite. Is it a simple coax cable like UHF or is there more to it than that?