Who gives a Sh@t what the law says. If you can do it then you can do it. It really is mostly a very simple thing to change a light switch or put in an extra power point. If I feel at all uncomfortable, I do the work, then I call in a Sparky to check it out.
Plumbing is almost entirely a no brainer. The only problem areas that might be encountered are when plumbing and electrical intersect.
The term 'grammar nazi' was invented to make people, who don't know their grammar, feel OK about being uneducated.