Thanks for all the replies.
Attached is a picture of the (almost) finished coop. All in all, pretty free from driven wind and rain, except you can see that there is a gap at the front of the gable end which I will fill in with timber.
There is also a gap under the ridge cap, along the roof line which is my primary ventilation. I want to keep the holes, so I will mesh underneath as suggested.
Under the eaves is a similar problem, and I think it will be more difficult to mesh it. If I simply fill it all in with timber than I don't think I will get much through ventilation. What dya think? Should I simply fill in under the eaves, or mesh?
Thanks,
Jim