Hi Juliette and Nick,
after thinking twice there is a way to have the PRS-505 menus localised to dutch and italian!
PRS-Customizer by JeffElkins will do it for you.
PRSCustomizer: Customize and personalize your PRS505 Reader
Both dutch and italian languages are integrated.
Downloadlink is in the refered post.
Nick: You would have to install the 1.1.00.18040 US-firmware before using prs-customizere.
If PRS-Customizer is applied you can change the language within the "About-Page" of Readers Menu. By pressing the "1" key
with "0" the clock in the lower right corner will be toggled.
PS: On the other hand the dutch and italian translation in PRS-Customizer's "main.xlm" as well as the dutch expressions in the PRS-600 menus could be used as a basic for translating PRS+, at least for the "sony-stuff" menus.