Opel ASTRA Owner's Manual page 206

204 Vehicle care
Low beam (1) outer bulb.
High beam (2) inner bulb.
Low beam (1)
1. Rotate the cap anticlockwise and
remove it.
2. Disengage spring clip from
retainer by pulling. Withdraw the
bulb holder from the reflector.
3. Detach the bulb from the bulb
holder and replace the bulb.
4. Insert the bulb holder, engaging
the two lugs into the reflector and
rotate clockwise to secure.
5. Push spring clip back in place.
6. Fit the cap and rotate clockwise.
High beam (2)
1. Rotate the cap anticlockwise and
remove it.