Thanks for that. Let me see if I've got it straight. First, as you go westbound into the OCA, you get a clearance from Shanwick Control (at Prestwick), to enter the OCA, and fly a certain pre-planned route (airway or otherwise) which gives you procedural seperation.
You're then handed on to Shanwick Radio (based in Ballygireen), who provide mointoring and traffic information based on the planned routes and reports from traffic in the area.
Presumably a similar thing happens going in the other direction into the Gander area, and the two talk to each other so that they know who's coming.
Is that about right?
Steve.