Réunion is a French Overseas Territory. There is no formal British diplomatic representation on the island. If you need consular assistance you should contact the British Embassy in Paris.
The cyclone season normally runs from December to April. You should monitor the progress of approaching storms and follow the advice of the local authorities. See Natural Disasters
Although there’s no recent history of terrorism in Réunion, attacks can’t be ruled out. See Terrorism
Most visits to Réunion are trouble-free. Crime levels are low, but you should take sensible precautions.
Take out comprehensive travel and medical insurance before you travel.