I think aircraft manufacturers (remember them) have some form of regristration/control sequence/system for their new types. Not that they've had any for many a year. Could not this a/c assume one of these non G- registrations say under bmaa or pfa design authority?
Err, no. You can put a serial number and G-XXXX registration on a double bed or canal boat should you wish, but it gets you nowhere with regard to airworthiness documentation. An aircraft manufacturer has to certify that something confirms to an existing approved design before it can fly, which isn't the case here.
I am however curious as to how the type never managed to meet someones approval be it ARB or whatever.
Straightforward enough, the particular aircraft class, at the time, CAA/ARB didn't feel a particular need to impose significant safety regulations on. Later they changed their minds. (A bit like what is happening to gliders at the moment.) Same would apply to any type which had only ever flown under military authorisations.
Final solution is to move it to France and only bring it back occasionally until we join the EEC for real
Right at the moment we're worrying about whether it's safe to fly on the occasional calm sunday afternoon - you want to cross the channel?
G