I occasionally check the italian tax website and there are now some updated tax guides, in italian, including tax for foreigners. All to be found here
Agenzia delle Entrate - Guide fiscali
and their English language site section
http://www1.agenziaentrate.it/inglese/
UK non resident tax guide last updated April 2008 downloadable from
http://www.hmrc.gov.uk/pdfs/ir20.pdf