It is quite likely that these STC items have been aproved as a minor mod , if the person who raised the minor mod ticked the box on the form to aprove it for all Cubs then if you can get hold of all the drawings and the mod number from one of the other owners in the UK then a licenced engineer can fit the STC under that mod number.
Thanks. I thought as much. The problem is always trying to find which aircraft has the mod!
It would be sensible for someone to hold a database of STCs approved as minor / major mods in the UK wouldn't it? Actually, it would be most sensible for the CAA to do that.
QDM