I'm not sure I can trust my electrician, what should I do?

[plugwash]

A common mis-conception, A six amp MCB will allow over a kilowatt of heat to be generated at a hot spot, such as a failing joint.

That is true.

However afaict we do not routinely inspect joints anyway. Even a PIR usually only checks a sample. One problem is that re-tightening joints can sometimes cause more problems than it solves

I really don't see much difference safety wise between a joint that is not accessible for inspection and a joint that is accessible for inspection but never happens to get inspected.

Fortunately modern plastics are treated with flame retardants such that while they will char they don't tend to catch light when joints burn out.

 

[Scoby_Beasley]

I'm personally thinking that, at a future date, a switch blows / SWMBO'd wants more d/lights and you call someone else in, they'll be mortified! You need to get it right now.

Previous wiring before 17th Ed supp 1 doesn't have to meet those specs.

Anything that is worked on / added to/ amended, does. NOW!!!