Val
Ryder Cup Winner
Generally speaking the train and bus scenario works well for Opens in Scotland.
Not sure about Gullane but Drem is only two miles away and I think the police close the Drem/Gullane road to all except buses.
Road comes out at the Fire Training School which is opposite the entry to the club.
Scotrail have a train/bus offer on. Price is normal off peak ticket + £5, buses from Drem to the course. £5 return on the bus is a bit rich though.