From the U.K. I want to send a box of books, cds, playstation, wires,
clothes etc. to a friend in Brazil. He will keep it for me, till I
move there in a few months. I found a courier company which ships
worldwide (ParcelForce) and they just state the service is door to
door.

I've been told that I should be very careful about sending anything to
Brazil. Most packages are inspected by customs and I can easily end up
paying 60% on the supposed value of the goods I'm sending. Another
possibility is that the goods are impounded for months and easily
damaged, compromised or lost.

So how do I safely send goods to Brazil in such a way that I avoid
paying any taxes? Note that all the goods I'm sending are for personal
use.

I am a Brazilian and I constantly send goods to parents and relatives.
 I would strongly advise you not to add any electonics and just ship
books and clothes.  Take the electronics with you.  When shipping, you
will need to fill out a customs form.  Just label it USED CLOTHES and
similar.  Books are OK.

According to Brazilian law, anything with a value over US$50
(including shipping and insurance) is subject to taxes, which may end
up doubling the price of the goods.  So, another tip is to avoid
shipping more than US$50.

The only exception for duties is for a Brazilian returning to Brazil.

Good luck!