Sunroof drain - Fine wire. Get the seats and carpets out asap. Check the drain hols in the bottoms of the doors. When it finally stops raining there pull off as much interior trim as you find necessary and dry EVERYTHING out. You could even have water in the loom up to the dash cluster (capillary attraction). Water in looms does funny things. If you really want it dry - drive over here to Perth 33+ and dry as a chip. The kettle is on!
Good - Fast - Cheap: Pick any two.
E23 735i; E30 318i; E32 735iL (X 2 - 1 Alpine White and 1 Glacier Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i