Feedback:
I got hold of some Rainx and sprayed it up this morning , only about half hour before I hit the water. I could see the drops run off the case when I tested it under the tap straight after however what showed up on the final pics taken were large water blobs , rather than several water marks as before. Overall it was better , but not as good as I had hoped.
Im going to re spray the housing and let it sit for a day or so before I hit the water next time and see if that makes a difference. I'm wearing the camera on my wrist so the camera is in and out of the water as I paddle in and take off so there is a lot happening, fast .