Hairyplane, I wouldn't hold your breath for the Speedsix to move back to Old Warden. It has been waiting for hangerage at White Waltham since the current owner acquired it. I know that he would acknowledge that Old Warden is an important centre for British aviation heritage and hopes to display the aircraft there as much as possible but it is not currently suitable geographically for him and the maintenance team.
The aircraft was delivered to Old Warden for last weekends Royal Aeronautical Society Garden Party which was a fantastic day. Roger is looking forward to displaying the aircraft on Sunday!
As for coverting the aircraft yourself, who can blame you but again don't hold your breath. The aircraft will remain in the Mills family hands for the rest of it's days. One of Roger's grandsons was trying the aircraft on for size on Sunday and he is only six months old! Like you he was thourghly impressed!