I am with Churchill and pay £480 for my import, they don’t ask for a tracker, and only difference between a UK and Import, is the import does not have an immobilizer fitted as standard, you will need to have one fitted, I had an Thatcham Cat.1 immobilizer and alarm fitted with auto door lock for £240.
The insurance issue I think is more to do with their computer systems not recognizing pre dated cars, as they can only see on their screen that the roadster goes back to 2004 (when the car was launched in the UK), but you are asking to insure a 2003 car !!!!!
The same for the coupe.