are you installing this on a stud wall (i.e plaster boarded) or is the wall solid concrete or bricks ?
well if its bricks/concrete you need an angle grinder channel maker and/or if your house is finsihed then the angle grinder is out because it will make alot of dust....
so you need patients and a club hammer (5KG min) and say a 2" bolster and work your way up this will make some mess but wont make anyway near the kinda mess a grinder will make, once you have made your channel and how deep it will be place the cables in some plastic like a carrier bag or if you want to be really professional use some DPM (damp proof membrain) but thats a little ott, and really you should cover them with a metal cover found from most electrical shops it costs about 6 quid for 3 meters and is 2 inch wide (but i would not honestly bother if it was a DIY job) get yourself some bonding and a straight bit of wood or metel and mix it up and bond the wall (not to thick you will need to filla it later and paint)
if its plasterboard you are pretty lucky because you can make a hole behind the tele (where your plasma will be) and work down to the middle stud (nogging that goes across (horizontal)) and make a small hole at the top and bottom through the plasterboard then cut out the middle bit (this should be about 3-4 inches up and as wide as you need for the wires to go around the nogging) you might need a chisel to take some of the wood out of the nogging (but this will depend on the wires and there thickness's) and once that is done just cover over them with some plastic (for example a carrier bag) and filla it.... you will never know you have any wires in the wall
also some older housed dont use a middle nogging so you might find that you can jut drop the cable down.
also there should be insulation in the walls which will make it difficult to feed the cable down the wall a good tip is to use some 10mm earth say 3 meters as this cable is pretty thick and will go past the insulation pretty quick.
when mounting the plasma you must find studs (wood going verticle up your wall behind the plasterboard) or your plasma could fall of the wall, they are normally 400mm from each other so if you find one you should find the next one easy with a tape measure (but they can be 600mm) and also depending on the chipie that built the studs they coul be any measurement as there is plenty of cowboys out there (should be 400)
i do this kinda thing alot and also i am putting a small plasma in my bedroom at the weekend so if you can wait i can show you an example on plasterboard