It is the usual old chestnut - no instrument qualification is required to operate IFR ourside controlled airspace in the UK but conditions need to be VMC however in the case of homebuilts the legislation specifically over rides the "usual" rule by specifying the aircraft may only be operated under VFR and therefore whilst you can be in VMC but IFR you can only be VFR in VMC. It is the aircraft that is the restricting element not the pilot.