DIY advice is a no-win situation.
Bank holidays are a particular problem 
We could just say: Regulations and calculations for this are quite tricky, but FYI most of the cost of your job is digging the B . . big Hole as no one really wants to do that. So get an electrician round, get sound advice on the route and depth of the trench and get some underground duct and draw rope and a spade. Arrange for Electrician to return when the hole is ready to fill.
i.e. Only pay electrician to do the electrician bits and both parties are happy . .
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I don't think the 'sheds' help to be honest, they're full of electrical stuff from an led lamp to a consumer unit, yet there's very little mention of the need to have things properly tested. I know it may be easy to swap a white plastic socket for a nice shiney chrome one, but what about testing it's safe, and I'm not just talking about the actual fitting of the socket, I'm thinking about the installation before you touched it, do you know if it's actually got a functioning earth?
I've seen an increasing number of older properties with earthing issues, I had one last year, TNS system that had gone fault on the incomer, Ze of 300 ohms, I had another where it was non existent, the landlord, an electrician allegedly, had decided to TT the supply even though it was a TNS system, if the tenant hadn't asked me to look at it then that installation would have been left unsafe, even worse was the fact that it was a looped service off next door, so they had no earth either.
Sadly I think that Joe Public has very little idea of how important the tests we do are, and a lot of them have no idea that we actually do any tests, whether this is down to the fact they don't see any testing, or perhaps there are a lot of electricians who'll change a socket or switch, or light fitting and not bother doing any testing, we've all been there, you find that there's no earth on something while working at a house and the customer replies, "well it works doesn't it".
I always make a point of explaining why we do a loop test, and showing the customer the test being done, and telling them the result, when you tell them that the maximum value is say 1.5 and there's is 0.50 they seem very happy, it's like you've told them they've got a really good car or something. The worrying one was several years ago, does anyone remember a certain DIY store that produced those handy 'how to' guides, everything from replacing a door lock to rewiring your own home! If I remember correctly the ECA was responsible for getting the 'how to rewire your home' guide, withdrawn, and quite rightly so.
I did a jacuzzi for a mate last year, he wanted to have a go, so fine, I went and looked at the job, did the calcs for the cable size, then gave him a list of materials and sent him off to get them. We arranged a day to do the install and I marked up where the holes needed drilling, where the cable was to be run and gave him the spacing distances for the cleats, and off he went, when the cable was in I connected it up, tested it and did the necessary paperwork, I was more than happy because I didn't have to do all the donkey work, and he was happy because when his friends came around he could tell them how he'd done most of the work, but he knew it was safe because an electrician had done the connections and testing.
I think we don't generally want to be seen as unfriendly, or elitist, I certainly don't at any rate, but then again I don't want to see anyone get hurt because they couldn't afford what I advised but did it anyway. By that I mean with particular reference to cable sizes, go anywhere on the web and you'll find tables telling you what current a given size of cable will carry. Unfortunately, when they see that a 2.5 t&e will carry X number of amps and is about 50p a metre, yet you've said it needs a 6 mm at £2 a metre, they often don't understand why you've said it needs a 6mm, be it for volt drop, or earth loop values or whatever, they just see cost. That is the bit I worry about, something going wrong, somebody getting hurt and all because somebody wanted to save a few quid, as I say when people go on about the cost of having it done properly, "you think this is dear, try pricing a funeral, or a house rebuild,because you could be looking at either or both, if it goes wrong.
