Britain is represented in Bhutan by an Honorary Consul. The nearest consular office is British Deputy High Commission in Kolkata. See Consular assistance.
There is a low threat from terrorism. See terrorism
You should arrange your travel well in advance. You must arrange any visit to Bhutan through an authorised travel agent. See Entry requirements.
Most visits to Bhutan are trouble free. In 2014 and so far in 2015, there were no cases of a British national requiring consular assistance in Bhutan.
Take out comprehensive travel and medical insurance before you travel.