I'd keep wiggling the key & wheel, do you have a spare key? Move the key up & down, side to side etc. Dont force anything too hard thouhg as you dont want to snap the key in the lock!!
If all that fails then this may sound a bit drastic, but remove the whole column and swap with another from a MK2 of the same age. Looking at your sig its a 90 spec right? So you'll need a 90 spec column from another car from your local scrappy. Try to get one with a key if you can, it will make your life easier in the short term and you can swap the lock barrels over later:
1. Take out all the ignition shroud trim & the dash undertrays
2. Remove wheel & stalks
3. Undo large bult holding the ign shroud to the column
4. Undo &
remove the nut & bolt holding the column to the universal joint at the bottom
5. The column should come out complete with the ignition switch housing
6. Now you can remove the ignition switch, which may need replacing (may as well anyway while its all out!)
7. To get the barrel out you need to drill a 3mm hole in a specific place, and press a locking tab in:
