There is not much public transport in Iceland so if you are without a car you will be reliant on taking organized tours to visit all the key Iceland activities.
There is no need to buy a SIM card for Iceland. Indeed my UK provider Vodafone covered me under my normal UK plan.
Most hotels have breakfast as part of their offer – and I would definitely make sure you get it included.
Wine is very expensive in Iceland. However, there are several ways around this.
There is a great website for looking at Northern Lights predictions which is the Icelandic Met Office. We found this quite accurate.