Hi,
I'm a sparky running my own business and I have plenty of thoughts on this topic.
Firstly, I will never (and now a company policy) get in a roof space without isolating the whole property first, should anyone else feel like getting in their own roofspace i suggest you do the same.
Problems with wiring arise largely from modifications of old systems without damaging wall finishes etc, I belive a large cause of electric shock in a domestic environment is caused by people adding onto what was previously installed, and not ensuring the continuity of the earth, a prime example of this is where the old VIR cabling was replaced to light switches, the existing conduit has been left in place which typically pokes up about 25mm higher than the ceiling joists, and when the switch cabling is installed can easily be trodden on, cutting into the insulation of the cable and rendering the conduit (and anything conductive touching it) live, another prime way of ballsing it up is to replace a section of the circuit with new cabling and not get the earthing right.
Now i'm about to get contraversial, in my opinion Australia has a terribly lackadaisical approach to the standards to which they teach tradespeople, please jump in and tell me to eff off if you have other views, but I believe the standards which electrical tradespeople are taught are totally substandard, the methods of electrical testing & certification (I know because I had to re-do a lot of my qualifications when i moved over here) are behind what I was doing in the UK 10 years ago, by at least 20 years. My argument, and believe me I like to spruik my opinion, is that unless you cannot absolutely guarantee you work is safe, it doesn't get energised.
Sorry if this should have been put in the "have a rant" section, but I am pretty fed up with following cowboys into jobs, fixing things that have been done badly and being labelled as 'overpriced'.
The insulation installers are generally just trying to take advantage of the oportunity to make a quick buck, can't fault them for that, but for christs sake take responsibility for your own actions, especially when they may endanger someone elses life.
New Page 2 if anyone needs an installation inspection.
Rich