You wouldn't ned a test, as you already have C1 on your licence by the sound of it, because of your age.
However anyone born after a certain time does not get this on their licence, and has to be trained and tested. Therefore there are plenty of companies offering this course. You could probably do an abridged one due to your experience and the lack of need for a DSA test.
I don't suppose there is any legal obligation to put you though the course, but I would have thought they would listen if you requested it.