Wall mounting 42" plasma on plasterboard (and hiding cables)

[Maxf]

I'm about to buy a 42" plasma, but (when mounting my speakers) I discovered that my wall is plasterboard, with a large cavity before it hits brick (I had thought it was just board directly onto brick). It is an external wall, but the flat is quite new so I'm assuming this is some method of insulation.

Any tips how to do this? I can't find a wooden beam anywhere to mount to, but I'm assuming with the right screws/plugs I can mount to plasterboard.

With regards to hiding the cables, I'm assuming that plasterboard has made this much easier - would it be madness to cut into the board and just poke the cables (hdmi, speakers, usb etc) in, before patching up? Sounds like a bit of a bodge though!

Finally, do people normally get a wall mounted plug socket put right behind where the TV is, or hide extension cables?

[Maxf]

I havent opened the wall up, but given the drill bit went through the plasterboard like a knife through butter and didnt meet any resistance, maybe 2-3" or more.

I'm thinking that I'll get a big hole cut into the wall, then some wooden blocks attached to the wall and the TV attached to these. So, in short... it's still on a stand below the intended spot