theres a fella on this forum called dan from that area who seems to be incredably knowledgeable about millisle fishing. Im sure he wouldnt mind dropping him a wee pm....
Donaghadee is a good spot although im not sure if they are still dredging the harbour at the minute. if so i would give it a couple of weeks to settle down
I like ardglass, although might be a bit far from you....plenty of mackeral in season as well as pollack coalies wrasse etc..... go to the rocks at the bottom of the golf course.
hope this has been of some use