Read the last article on this page - the writer suggests a back street electrician. I have done as he suggests (at a cost of £17 including parts), however, that was after trying for an hour to wreck the switch. http://www.letsfixit.co.uk/html/vacuum_cleaner_faq.html
There is also a tool available on http://www.vacuumcleanersparesuk.co.uk/acatalog/dco4.html
Hope that helps.
David C, May 2007