With the atrocities that occurred on Friday in Tunisia anxieties are understandably high for people who have holidays booked. To know where you stand with regards to cancelling/postponing/refunds the advice is to speak to your tour operator. The Telegraph has published this article today:
www.telegraph.co.uk/travel/travel-advice/11701869/Tunisia-travel-advice-for-tourists-after-terrorist-shooting-in-Sousse.html