When using BSI online, search for BS 7671:2001 - that's the standard number for the latest version of the IEE wiring regs. However, I'm not sure whether BSI do a pdf version.
which sells a hyperlinked pdf version on CD-rom, bundled with some guidance notes and Word6 versions of all the forms. The bad news is it costs £350 for a single workstation licence and £1000 for a site-wide licence.