Have you considered the Flybe flights out of Terminal 2 to Edinburgh? T3 -> T2 is an easier connection (quick walk underground), and there's a slim but real chance that as Flybe becomes Virgin Connect early next year that some integration may happen by March. I wouldn't expect Virgin Connect to move to Terminal 3 or have SkyPeso mileage earnings by then (though I would expect the first the long-term and the second in the medium-term), but it's possible you'll be able to recheck your bags with VS in Terminal 3 and have better rebooking protection in the event of IROPS. I searched a random Sunday in March, and it looks like there's an 11:20am flight (2hr35min connection) which combined with the quicker transfer makes this itinerary more feasible.