drilling through walls/pipe and live wire detectors

[abstract]

i live in a maisonette and i need to drill some holes as im putting up some shelves,the wall im going to drill into sounds solid,but im a bit apprehensive as im wondering whether its possible that pipes,electrical cable lie underneath.
i was thinking of buying this or similiar

http://www.argos.co.uk/static/Product/partNumb er/0072784/Trail/searchtext%3EDETECTOR.htm

but it states that the detection depth is 25mm for copper cabling and 50mm for AC wire and studs. my screws are 2 inch/50mm long,so the hole that i need to drill to accomodate the plugs would have to be longer(roughly 60mm) now my questions are no.1-do these detectors work? no.2- as i need to drill further then the detector can detect,is there any point of buying it? no.3- how likely is it that there woiuld be AC wire/gas pipes etc.. in a (what seems to be) solid wall? (its at the back of a built in storage cupboard with the neighbors identical cupboard behind)

CHEERS IN ADVANCE!

[Glencraig]

My first answer to this would have to be:- "if you're not sure about the location of pipes & wires, then call in a professional".
"Yeah, right" I hear you say and you've probably started drilling already by the time you read this.
Buried wires should always be laid either vertically or horizontally, usually vertically but never diagonally and should either be in a conduit or at least covered by some kind of capping. Pipes, be they water or gas, should also be vertical or horizontal only.
Therefore, if there are any switches, sockets, taps or outlets on the wall in question then don't drill anywhere above/below them.
There could, of course, be radiator pipes buried in the walls but this is unusual.
Regarding pipe/cable detectors, you get what you pay for with these but they do generally work as advertised.
Finally, drill carefully and you should be able to feel a sudden change in the density of the wall if there is anything buried in it.

[abstract]

cheers glen!