How do you remove ignition switch from 318 BMW?

Ignore what Haynes tells you to do, (ie using a 1.2mm probe).

Buy a new switch from your BMW dealer, you will see a spring loaded catch on the barrel.

Remove pastic cover on under side of steering column, Using the new barrel as a template, drill a 4mm hole on the underside of the aluminum casing, this will expose the spring loaded catch, push the catch in with a small screw driver and extract the old barrel. Fit new barrel.