Common existing problems with installations going back to the late 1950's and early 1960's and they are beginning to require some TLC.

The main problems I’m finding are:

Problem -The lighting circuit(s) do not have a protective conductor.
Effect - Metal light fittings or switches may become 'live' in the event of a fault.

Problem - The 'ring main' power circuit(s) are wired in buried metal conduit without a separate protective conductor.
Effect – After some 40+ years, corrosion is starting to manifest itself with increased resistance in the protective path with the result that circuit protection will not be as reliable as it could be.

Problem – The cooker circuit is wired in the 'minimum sized' cable required.
Effect – Today's appliances are used more than when the wiring was installed, the volt drop will exceed permitted limits.

Problem – Water main often used as main protective electrode and plastic (non-conductive) pipes are used today as replacements both inside and outside in the road.
Effect – Circuit protection may be compromised.

So, having got this far, the question you are asking is ' what does it mean and how do I know?.

You do have your wiring checked at regular intervals, don't you? (every 5 or 10 years)
Is your fusebox metal and battleship grey?
Do you have re-wireable fuses?
Do you have unswitched sockets?
Have you had electrical work carried out in say, the last 10 years, without a certificate being issued?

It has been known for 'special offer replacement fusebox' to be done without a certificate or any remedials required being pointed out or being done. As they say, you get what it says on the box – new fusebox – that's it!

Just to reinforce this, just the other day I was called to install a new heater in a bathroom. Property built in 1956, but I had a feeling in my water (it’s a man thing, girls!) that something wasn’t right. Nice new fusebox installed ‘about 4 or 5 years ago). Bravely, I felt the cables coming out of the floor to find them to be lead sheathed rubber insulated cables. Took a light switch off to find the perished rubber insulation taped up. Asked if the ‘electician’ said anything ‘yes, he suggested I had it looked at’!
Customer felt that as the lighting cables were in 5/8 slip tube (I’ll be asking questions later!!), all must be well as they are protected. Needless to say I declined to go any further unless something was done. So far, nothing.

If you think you might have a problem 'lurking', then contact your regular electrician for his advice.

If you don't have one, then give me a call. Advice/opinions are free, but if I get my tools or testers out, then a charge will be made.
As a guide, a PIR (Periodic Inspection Report) should cost between £200 and £350, depending on the amount of work found necessary to identify.
Currently, the new 'Home Information Pack' does not demand one, but be recommended, as the inspectors will only be trained to spot if lights/sockets work!

Frequently, casting an 'experienced' eye over a property will identify the obvious problems (see above!).

The ‘new’ BS7671 was issued on January 1st 2008, actually published in mid January, came into effect on July 1st 2008 and the 1st corrections came out in June 2008 - really!

We are not sure what effect this will have, but concerns have been expressed concerning the possible requirement that if cables are not at least 50mm below the finished surface (that should cause a weakness in most 100mm thick walls), or protected by earthed metal etc., then a 30mA RCD should be provided.
We (the ‘working trade’) are hoping that these sort of ‘queries’ will be addressed by the next amendments.

I hope to keep you up to date, if/when the mud begins to clear. The good thing is that the current BS7671:2001 (amended to 2004) is not unsafe and could be used until things become resolved.
Afterall, the IET have never issued an unsafe set of wiring regulations, it’s just that our requirements have moved on.