Flexible Use Airspace is defined in CAP 740 and applies to military/civil arrangements and certain other activities. There is nothing within this policy that provides for shared use of regulated airspace for VFR operations. Whilst CAP 725, the Airspace Change Process requires sponsors to apply FUA to new regulated airspace this is largely ignored because the published FUA policy is not relevant to terminal airspace.
Working with the CAA, FASVIG would propose a new FUA policy for VFR use of regulated airspace.