We will end our Rick Steves tour in Belfast, but we want to go to Scotland afterwards on our own - particularly to see Edinburgh and the highlands around Glencoe. Is it better to try a ferry or to fly? If flying, which airlines should we look at?
I would fly. It’s a short flight, so pick whichever flight gets you there at a sensible time. There isn’t much to choose between the airlines - just make sure that you comply with their baggage policy.
Ferry + Bus makes for a very long journey. Flying is the no-brainer. I'd look at all three of the airlines operating the route non-stop, and weight schedules against total costs (fare + added fees)
The ferry takes you to Cairnryn which is a long way from where you want to go. Catch the plane.
Reading the Scotland forum you are talking about also hiring a car and visiting Wales and England, ending in Bath and then London - Is that still part of the plan?