AIUI, the CAA is out of the picture now as far as the initial acceptance goes.
If a type has been previously on any EU register than it can go on any other EU register now, under EASA.
I am suprised to find Jetprops on EU reg - interesting! Never thought this was possible. The conversion is done under an FAA STC so somebody must have done the paperwork based on that.
I suggest contacting the owners directly.