I don't know how much it varies by nationality but I have had loads of UK passport holding family here and there are no restrictions. I use Al Maha meet and greet to save my family having to queue up and pay for the visas, they just get taken off the plane and processed in a VIP lounge although that is just a room with chairs and orange squash! You can book it at the airport, they need at least 24 hours notice and the full name, nationality and flight no of the passenger.