I'm a British Citizen traveling to India, connecting flight in Oman, do I need a transit visa?
Per Timatic, the database used by Airlines:
TWOV (Transit Without Visa)::
Passengers with a confirmed onward ticket for a flight to a third country within 24 hours. They must stay in the international transit area of the airport and have documents required for the next destination..
So if you're on a single ticket, you do not need a visa.
If on separate tickets, you can get a visa on arrival or an e-visa in advance.