This is what the UK Foreign & Commonwealth Office say about travel to Sri Lanka: Information for families affected by the tsunami can be found at Sri Lanka: Information for Families.
We advise against all but essential travel to the north or east (other than Trincomalee, Nilaveli and Arugam Bay, but travellers should be aware that most hotels in these areas are closed because of damage from the tsunami). Much of the north and east of Sri Lanka remains heavily mined, particularly around the A9 road to Jaffna.
The recent tsunami resulted in extensive damage and large numbers of casualties on the south-western, southern and eastern coasts of Sri Lanka. A number of hotels and resorts on the southern and south-western coasts have now reopened. Anyone planning to travel to these areas should check with their tour operators and/or hotel before departing to ensure their hotel is operating normally. Most hotels in the eastern towns of Trincomalee, Nilaveli and Arugam Bay have yet to reopen. (For further details please refer to the Natural Disasters section of this Travel Advice).
There is a threat from domestic terrorism in Sri Lanka.