It is also advisable to run the battery down, and fully charge it occasionally to extend the battery life. If you run a laptop permanently from the mains, you can find that the battery will stop working, and will need to be replaced.
Many thanks to you pcwork and mattie. Both your answers have been really helpful. The laptop has only been operational for a few weeks so hopefully I haven't done too much damage to the battery yet. Will run down the battery and fully recharge it regularly in future.