Regarding W+B being "done"...something I've always wondered (and this is very obviously only applicable to private operations, not commercial) is to what degree this "doneness" is.
Opso92, I've just had a good look through the regs (including those CAO references provided by JT, above), and can tell you this:
If your operation is not RPT, and your aircraft is less than 5,700 Kg, then the only thing you have to do is:
Ensure that:
1. Your aircraft is loaded in accordance with the approved loading system;
2. The takeoff and landing weight is less than the maximum;
3. The CG is within limits for all stages of flight;
There is no requirement for any paperwork. The only requirement is for you to
ensure the above things. Of course, you may get a smartarse FOI that wants to know how you managed to "ensure" those things without paperwork, but such a question has no legal support.
From the legal point of view, they would have to prove that you did not load in accordance with the loading system, or that the takeoff or landing weights were exceeded, or that the CG was out of limits.
They can't take you to court on the grounds that they didn't like your explanation about how you
ensured everything.
For example, you could say that you consulted the local clairvoyant before undertaking the flight. The FOI wouldn't like this, but couldn't take you to court on this because it does not prove that you didn't ensure!