As it will be maintained to the equivalent of the permit to fly, all aircraft under that I believe are VFR only, however the Vulcan managed to get an IFR clearance I think. The Dak as an ex commercial aircraft will possibly not be operated under the Permit requirement.
I saw some poor Cessna today awfully low (on the way to Cosford) obviously struggling along VFR under a really low and diminishing cloud base.