How's that for Christmas spirit, mooncow! No one has replied thus far. Here goes.
8 It's a double def. Think "school" in the sense of marine life.
12 I can't actually remember how the wordplay parsed at this distance but the def. is the first two words, such as a roar.
I agree with you about the construction and the way the top line fits. The really clever bit is that there are perhaps two different 12-letter names for the thematic location and both the right one and the wrong one create real words when added to the down solutions.