Be aware each region England, Wales etc has different rules as far as the law goes. But the regulations are not law, but can be used in a court of law, and the regulations define a "Competent person. A person who possesses sufficient technical knowledge, relevant practical skills and experience for the nature of the electrical work undertaken and is able at all times to prevent danger and, where appropriate, injury to him/herself and others." if you are not competent you should not do the work. So regulations wise if you have the knowledge then you are classed as an electrician, there is no exam or test which makes one an electrician, although having the bits of paper makes it easier to show others that you have the skill.
So any work done is split into three sections, design, installation, and finally inspection and testing. It is the inspection and testing where the DIY guy in the main falls down. There was a case on the death of Emma Shaw where the courts rules an electricians mate did not have the skill set to do the inspection and testing, so the foreman was found guilty for using unskilled labour. So was responsible for her death. I am not saying I agree with the court, but the case resulted in reduced use of electricians mates.
Even as an electrician in my own home I don't have the meters required to complete a minor works certificate or an insulation certificate, and every job should have one or the other completed, what I lack is a meter to measure the time it takes for a RCD to trip, and a meter to directly measure the loop impedance, I can measure resistance and calculate the loop impedance from the readings give on existing certificates, and I can measure insulation resistance, but the full test set would cost around £60 even to hire, to buy looking at around £500, since they need calibrating these test instruments always belonged to the firms I worked for, I could borrow a set from work or my son, but I don't have them at home, so technically I can't complete the minor works certificate so should not do the job.
However we all know I will do the work in my own home, and I have enough experience to know when I am sailing close to the wind and I need to hire, and when it is extremely unlikely I am out of the permitted limits. However if I make a mistake and some one goes to hospital as a result the hospital is duty bound to report it to HSE and they could pay you a visit and ask to see the paperwork, and inspect themselves to work out how the accident happened, if work related then they may visit, if not work related unlikely unless a death has resulted.
So postman, social workers, gardener, plumber, etc clearly do visit your home, and if the get a shock it is in their place of work, so electricity at work regulations kick in. But keeping strictly within the rules or law we would never move, or at least not exceed the 20 MPH speed limit through built up areas, can't even go to the loo without paperwork.
So you have to decide how much you feel safe doing. if every one kept to the rules this forum would not exist, I will fill in a minor works certificate at work, but never bother at home, I will test of course, but not all the tests the rule books say I should do. I know how to prove dead, but rarely follow the procedure to the letter, I have a portable power supply so I could use that and a proving unit, but I don't only one job have I ever been required to carry the proving unit and voltage tester around with me, we all break the rules to some extent.
So what I am saying is the most important thing is to use common sense, may be the wrong name, as not very common.
