I have a solution for Squealing Screws.

Here in the US, our thrones are sealed from leakage with a wax ring. It is a very soft wax and sticky. I went to the chemist and obtained a very large mouth drug bottle. (Free. No matter how much I protested.) I took one of these toilet sealing rings (About $3.) and put it into the drug bottle. (Put the ring in an EMPTY beer can and warm it with a propane torch.) It is strongly advised to drink the beer.

After the wax has cooled I dip screws into the wax before driving them. The wax is an excellent lubricant.

(Serge: The tip has been submitted.)