how do I repair the spring return on a dyson dco5 vacuum cleaner?

Not what you want to read but I've been hit by a few trying repairs.
You don't, take it to a shop it's a dodge job the spring could re-coil when you take out the unit and that could be dangerous some are open end reels ie: the spring is open and could fly out.
I called these mechanisms operation buttons 'idle buttons' simply because I considered the customers who came to my brothers stall to have these units replaced not repaired they bought them because they were too idle to wind the cable by hand. They thought it was funny and an old 'git' at 50.
Oh! never worked on Dyson.

Nobby
January 2009