SYDNEY/LONDON (Reuters) – Global insurance firms are circling Iran for business opportunities following the lifting of sanctions – and the first test of their appetite could come in March when some Iranian companies seek new cover. Insurers, the reinsurers that share their risk and the brokers that forge deals are exploring ways to tap a market worth $7.4 billion in premiums after a nuclear accord between world powers and Tehran led to the removal of restrictions on financial dealings with Iran this month.