Also in the US the 6 books of The Dragon Mage have been split. Books 1 -3 make up a trilogy under the series title of The Dragon Mage, whilst Books 4-6 make up the final set, under the series title of The Silver Wyrm.
However, I have recently noticed on the Wikipedia article on Katherine Kerr that the Silver Wyrm now has a 4th book, called The Silver Mage, due to come out in 2009.
I would gather that this would be book 7 of The Dragon Mage in the UK editions.