I think RoadRabbit has it 100% correct, the VOR radials are set in stone, or more precisely their aerials are set in concrete on the roof of the building.
So from a practical point of view, if you were flying from Donegal to Belfast, via Londondery, the first part of your flight you would only look at your Compass / DI, and fly approx 95 degrees magnetic. Then for the Londondery to Belfast leg, you would only look at your VOR meter, which would be set on the 314 VOR radial. Your DI and VOR will read differently.
.