Vd;

With no Ign Key, alternatives are limited (as well they should be, because that's the point!), but as a less violent alternative than taking power tools to the Ign Switch, the Ignition Lock Cylinder could be picked by a competent locksmith, or... another trick of qualified locksmiths, a key-by-impression made, but this requires proper key blank (I have these available)..., to allow turning of LC to the Ign ON Pos (3, NOT Accessory Pos 1 as stated earlier in this ancient thread!), so that LC retaining button can be pressed and LC removed normally.

See: http://www.sw-em.com/Broken%20Vintage%20Volvo%20Ignition%20Key.htm

Cheers