[heero_yuy]

The real problem in the walls is that although they are hollow there are usually cross members ( noggins ) at intervals between the vertical studs. You can use a stud finder to locate them but you then need to get the cables round them by making a hole in the wall at the noggin location and notching the noggin for the cable before re-filling the hole. There will also be a "wall plate" (timber) top and bottom running the entire width of the wall.

Depending upon the construction there may also be insulation beteen the studs as well.

You'll also need an electricians fish tape to pull the wires through.

When I wired up my place I ran the cables in the floor space and then put flush pattress boxes just above the skirting boards. That way the only cable in the wall was behind the skirting boards which are not plastered but nailed to small stand off timber laths. Then there was only a couple of inches actually in the plaster of the wall. Easy to chisel out and re-fill.

I actually had a route from the ground floor to the first inside some plaster boarded pillars that were where a dividing wall had been removed. I deliberately didn't put cross timbers inside these for the very purpose of pulling wires and pipes through.

If you have a cupboard under the stairs this may be the route you can use. I've home run all the CAT5s to a patchboard here that sits next to the router.

I did all this before I got my current router ( Buffalo air station ) that has a very good WiFi signal throughout the house and into the garden. Streams Go TV in HD very nicely.