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professional rewiring electricians in London

If you are not sure or have any doubts about the electrical condition of your property, the first thing you should probably do is hire an electrical inspector who will conduct electrical tests and tell you for sure if rewiring is needed. 

However there are some obvious things that can help you to make your decision, such as:

• If you have an old rusty consumer unit/fuse box which would usually have old coloured fuses, with only a few circuits which are not separating the ground and first floor for example. Meaning that one fuse is controlling all the lights in the premises. As well as lack of RCD’s, addition protective fuses which automatically disconnect the power in the case of live wires being touched. 
• Aluminum or incorrectly colored cables might indicate that the property has not been rewired since at least 2006 when the colour coding of cables changed from black to blue indicating the neutral cable; and from red to brown indicating the live cable. Spotting aluminum cables is easy enough as it should be written on the cable itself at every 12 inches. Aluminum cables are simply less conductive and break much more easily. 
• If you are experiencing electric shocks from any metal conductive parts in your house, such as metal light switches, lights, an extractor hood or even from a sink or bathroom; It might indicate that the circuits in the property are not earthed or are damaged somewhere resulting in some parts of your property being live.

Your homeowner's insurance will cover your electrical wiring, but the coverage may vary depending on several factors. If you know that your home is older, you will need to get electrical rewiring.

This will not only help minimize your home insurance premium, but it can also protect your home against fire and accidents. 

Not necessarily. The electrics might work fine and there is no rule that says a house from the 1970s requires rewiring. But before any conclusions can be made it is always a good idea to conduct an Electrical Installation Condition Report.

This report will identify any problems in the wiring; and would need to be resolved as soon as possible. The results of this report will also suggest what can be improved for the safety of the customer. There are, however, a few signs that can attract your attention even before an electrical check and might indicate that it is time to rewire your property.
 
One of them is if you have an old grey fuse box. It can work just fine, but lacks an additional protection function which are installed by standard practise in every modern consumer unit. Which means that if a person were to touch a live wire or surface that was not earthed, the supply will automatically be disconnected which could potentially save his/her life. 
 
Consistent fuse tripping or power cut outs might also be a sign that there is almost certainly a problem with the existing cables. The electrical inspection must be done in such instances as old cables might overheat from excessive usage which is dangerous and could potentially cause fire.
 
Consistent burning smells, buzzing or sparks is another sign. Old cables might smolder in the ceiling or loft where you might not see them but the smell will alert you and such smells should not be ignored. As well as sparks or buzzing, old wires over time might become loose at the connection points or even break causing big sparks which might inflame the insulation or plasterboard around the property. 

In theory electrical wiring can last up to 100 years or more. 
 
But what really matters and will determine the life span of electrical wiring is the condition of the outer sheeting of the cable which usually lasts around 50 years.
 
Other factors like how well your house was built and what type of insulation and thermal protection it has also determine how long your wiring will last. As wiring in the shed which is usually not so well protected from moisture and other external factors will obviously combust faster and would require rewiring more often.

Normally sockets are installed on a ring circuit on 32amp breaker , which means that the ring can withstand around 7200 watts.
 
In theory you can put an Infinite amount of sockets on one ring, but in practice the amount should not exceed 20 outlets.
 
It is counted in a way that each socket is assumed to use around 1.5 amps at max even though the socket outlets themselves are rated at 13amp, so much more power can be drawn from one individual socket.
 
So even if all 20 socket outlets are used at once it will not exceed 30 amps and will not make the breaker trip leaving you without power.
 
To give you a real life example your normal phone charger would normally use only 2 to 6 watts of power, whereas a normal kettle around 1200 watts. So if you would decide to use all 20 of your sockets to boil water, the breaker will trip as the drawn power would exceed the limit of 7200 watts, but in normal conditions you are safe.

In order to earth your electric system, first you need to make sure that your house is earthed.
 
For that you need to install a ground rod preferably in the location closest to your consumer unit. The rod can be installed at any distance from your house but should go 2.4 metres deep into the ground. After the rod is installed, a 16mm ground wire should be connected to the rod from one end and to an earth bar in your consumer unit and the other end. 
 
From that point on, all the earth cables from each of your circuits must be connected to the same earth bar in your consumer unit.
 
In order to insure that everything is done correctly a professional electrician should test the connection and inspect each circuit.

Yes you can, but not as easily. There would be insurance companies that would not insure houses with aluminum wires. Which is simply because aluminum wiring got a bad reputation due to it not accounting for aluminium and copper differences, electrical wiring was done incorrectly leading to problems with overheating therefore creating a fire hazard.
 
There are companies that would still give you insurance but it will take a few extra steps. One of them being an electrical inspection which will confirm that special types of connections and panels were used. And the cables must meet all the standards and pass all the tests.

By itself old wiring has no direct influence on your electrical bills. However, old wiring can indirectly affect your power usage through defective or incorrect wiring; a damaged thermostat/appliances or underground wiring.

The best and only sure way to check if the house is grounded is to invite an inspector and conduct electrical test. As even if you have earth wires running from consumer unit, it doesn’t mean that they are continuous and are properly installed. So it is better to check them to be 100% sure.
 
However, assuming that everything is connected correctly you can tell if your electrical system is grounded if you see a yellow and green wire coming out of your consumer unit, as well as one being connected to your water and gas pipes.

Aluminium wiring is not bad it is simply different and not as good as copper. However, if properly installed and used with the correct equipment it can work just as good and as safe as copper wiring.
 
The biggest difference of aluminium wiring is its softness, the way it corrodes, contracts and expands compared to most commonly used copper wires.
 
If all the differences as taken into account by an electrician and used with the right connections and panels, aluminium wiring is not as bad as you might of heard.

It can be done but only with a special splice connector. The biggest problem with mixing the two is that when different metals touch one of them starts to rust much faster than the other.

Rust will cause wires to break and not conduct electricity as well, as well as lead to short circuits and spark fires, which is very dangerous. It is always a good idea to replace any aluminium wiring with copper wiring as it is safer and it will last longer.